Correct for a manually set up carb, that is an average that fit with my
other 'made up' 5 turn or step number. (I could be close to right with
the 5 thing)

I have seen them vary usually from 2-3 turns for a minimal emissions
hooked up and tight lines to a couple really liking 3.5 - 4.25 turns and
they were tight too. Different years of carbs can be different.

The shape of the vacuum lines and emissions system can make a major
difference too.

Every time I put a carb kit in, the settings change on my manual setup.

I also find that at the above settings or the best lean idle according
to the book, the engine just purrs at 750 rpm. Not a ripple in a beer
sitting on the air filter.... The sniffer don't like that much....

I end up going 1/2 to 3/4 turn lean and having to up the idle speed
screw a little to keep 750-800 rpm to have it 'rumble' a very little for
the emissions sniffer.

If the computer is in the circuit, then the screws need to be out far
enough or 'close' to full rich so the stepper motor is pulsing even in
the middle of it's throw with a fully warmed up engine.

I have seen either 5 or 7 turns described for 'full rich' on the BBD
which kinda goes with the two settings I have seen for the finished idle
mix.

If the idle tubes are oversized, the screws can be at 1.5 turns or even
lower for a manual setup, but same thing goes for calibrating the
stepper, you still want the stepper perfectly in the middle.

I would want a freaking sniffer on the tailpipe to try and calibrate the
stepper.....

You 'can' force the stepper to go no more rich with the mix screws
period, have heard of lots of folks doing that, but it isn't the best
for running, same as the 'manual lean it a bit for emissions', I put it
back smooth when I pass the test.

I normally disable the computer on these carbs and manually set them and
we all have passed emissions.

I got 15 ppm HC and 0.16% CO on my last pass and I don't need or have a
cat.....

I do have an Accel SuperCoil on it for a hot spark though.

Mike

KurtS wrote:
>
> OK. So Factory Settings should be in the neighborhood of 2.5 turns out from
> full travel in, correct?
>
> > From: Mike Romain <romainm@sympatico.ca>
> > Organization: Bell Sympatico
> > Newsgroups: rec.autos.makers.jeep+******
> > Date: Thu, 07 Aug 2003 12:23:31 -0400
> > Subject: Re: CJ7 barely failed emissions
> >
> > Not kidding, really....
> >
> > Here is how I see it working. If I am mistaken, I would appreciate the
> > feedback.
> >
> > The OP stated he has a 'stock everything' 85.
> >
> > I therefore do not assume that the carb has been drilled or cut up to
> > access the idle mix screws.
> >
> > The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
> > full lean.
> >
> > The carb if manually set up has 'say' 5 turns on the mix screws from
> > full rich to full lean.
> >
> > With a perfectly working system, either the stepper or the mix screws if
> > a manual BBD operate approximately in the middle of the range or at 2.5
> > turns out for the screws or jumping from step 2 to step 3 to get the O2
> > sensor to read correctly with the computer.
> >
> > Now we toss in a partially plugged idle tube or something else gummed up
> > forcing a lean to 'some' extent.
> >
> > If I am manually setting the mix, I then need to open the mix screws to
> > 'say' 3 1/4 turns out to get it stable.
> >
> > In comes the stepper motor on the computer BBD. It has a choice of
> > either the 3rd step or the 4th step.
> >
> > It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
> > tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
> >
> > It keeps jumping back and forth between step 3 and 4. Every time it
> > hits step 4, it goes rich, a lot more rich than it goes lean when on
> > step 3.
> >
> > Bingo, a carb that 'just' fails emissions by being slightly rich.
> >
> > I also believe this is one of the main reasons you see the mix screws
> > cut open. Forcing a mix change via the manual mix screws can make the
> > O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
> > was from the factory so when it samples it is an even 2 step to 3 step
> > pulse which puts the mix back into emissions range.
> >
> > This is just fixing the symptoms, that blocked idle tube is still
> > there...
> >
> > Mike
> >
> > bllsht wrote:
> >>
> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
> >>
> >>> I don't think the computer is that smart.
> >>>
> >>> I think when it sees a lean it can overcompensate.
> >>
> >> I hope you're kidding...
> >>
> >> The computer monitors O2 content of the exhaust. It alters the mix to
> >> achieve
> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
> >> smart.
> >>
> >>>
> >>> The OP was only slightly over on CO.
> >>
> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
> >>
> >>>
> >>> The stepper motor only has so many steps. The proper mix could be a
> >>> half a step leaner than the computer sets it.
> >>
> >> Which is why I said the mixture screws are probably too rich. If the stepper
> >> motor has reached it's lean limit, then the mixture screws are set too rich,
> >> or
> >> something else has gone wrong in the carb to cause a rich condition. The
> >> computer will not cause it to be too rich.
> >>
> >>>
> >>> Mike
> >>>
> >>> bllsht wrote:
> >>>>
> >>>> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
> >>>>
> >>>>> You are right, but blocked idle tubes can 'easily' make the mix go out
> >>>>> of the computer controlled stepper motor's pins travel range.
> >>>>
> >>>> Blocked idle tubes cause a lean condition. The computer will try to
> >>>> correct.
> >>>> If the mix is so lean it's out of the stepper motor's ability to correct
> >>>> the
> >>>> mix, it's still too lean.
> >>>>
> >>>> In the post I replied to, you said "Too rich can be caused from partially
> >>>> blocked idle tubes." That's not true.
> >>>>
> >>>>>
> >>>>> They adjust the air flow only, the mix screws are set at factory rich
> >>>>> and plugged off.
> >>>>>
> >>>>
> >>>> The idle mixture screws are set correctly when the stepper motor is moving
> >>>> in
> >>>> and out near the middle of it's range.
> >>>>
> >>>>> When the tubes really crap out, you have to remove the spring from the
> >>>>> idle speed screw in order to get any idle at all. It goes out of
> >>>>> range....
> >>>>
> >>>> That's because it's so lean you have to open the throttle to keep it
> >>>> running.
> >>>>
> >>>>>
> >>>>> When I see a carb with the idle speed screw compressed tight, I
> >>>>> immediately suspect partially blocked idle tubes.
> >>>>>
> >>>>
> >>>> Yes, because it's too lean and they're trying to keep it running.
> >>>>
> >>>>> Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
> >>>>> and the spring is compressed or about 3/8" long.
> >>>>>
> >>>>> If you can get at the mix screws, you can force the carb lean with
> >>>>> them, That can pass emissions usually but doesn't address why it is
> >>>>> running rich, just the symptoms.
> >>>>
> >>>> There aren't many Jeeps with carbs running around that still have sealed
> >>>> mixture
> >>>> screws. By now they've all been cut, drilled or whatever. It's probably
> >>>> too
> >>>> rich because somebody's been f*ing with it and don't know what they're
> >>>> doing.
> >>>>
> >>>>>
> >>>>> Mike
> >>>>>
> >>>>> bllsht wrote:
> >>>>>>
> >>>>>> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
> >>>>>>
> >>>>>>> Too rich can be caused from partially blocked idle tubes. The computer
> >>>>>>> will set the stepper motor rich.
> >>>>>>
> >>>>>> It doesn't work that way. The computer will correct the mixture (lean or
> >>>>>> rich)
> >>>>>> to achieve the "proper" amount of O2 in the exhaust.
> >>>>>>
> >>>>>>>
> >>>>>>> See this link:
> >>>>>>>
> >>>>>>> http://www.off-road.com/jeep/tech/engine/carter.html
> >>>>>>>
> >>>>>>> A bad charcoal canister can also cause that, but with a bad canister,
> >>>>>>> the idle will 'usually' surge up and down a little and you will get
> >>>>>>> spits of oil coming into the air filter from the valve cover vent.
> >>>>>>>
> >>>>>>> Mike
> >>>>>>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> >>>>>>> 88 Cherokee 235 BFG AT's
> >>>>>>>
> >>>>>>> bllsht wrote:
> >>>>>>>>
> >>>>>>>> High CO = too rich. Lean out the idle mixture a bit. You didn't fail
> >>>>>>>> by much,
> >>>>>>>> so it shouldn't take a big adjustment.
> >>>>>>>>
> >>>>>>>> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
> >>>>>>>>
> >>>>>>>>> '85 C7 258 - computer in the loop - stock everything
> >>>>>>>>> Damnit. I should have know better than to take my Jeep in for testing
> >>>>>>>>> on a
> >>>>>>>>> rainy day but I did it anyway (it's a bit sluggish in wet weather). So
> >>>>>>>>> here
> >>>>>>>>> are my results:
> >>>>>>>>>
> >>>>>>>>> HC PPM Idle - 223/300 -- Pass
> >>>>>>>>> HC PPM 2500 RPM - 103/300 -- Pass
> >>>>>>>>> CO % idle - 2.10/2.00 -- fail
> >>>>>>>>> CO % 2500 RPM - 1.58/2.00 -- pass
> >>>>>>>>>
> >>>>>>>>> I barely failed CO at idle -- seems all my idle readings are much
> >>>>>>>>> higher by
> >>>>>>>>> ratio. I have been doing mostly city driving for a couple months.
> >>>>>>>>> Would an
> >>>>>>>>> hour or so on the highway take care of the high CO? Any other hints? I
> >>>>>>>>> replaced the EGR and O2 sensor about 3000 miles ago.

 

bllsht wrote:
>
> In message <3F327D03.CA7F4D39@sympatico.ca>, "Mike Romain" wrote:
>
> >Not kidding, really....
> >
> >Here is how I see it working. If I am mistaken, I would appreciate the
> >feedback.
> >
> >The OP stated he has a 'stock everything' 85.
> >
> >I therefore do not assume that the carb has been drilled or cut up to
> >access the idle mix screws.
>
> Well, I took 'stock everything' to mean that it had all the 'stock' equipment on
> it. If he had said it had never been f'd with, then I might have thought the
> plugs *may* be there, but still wouldn't expect it.
>
> >
> >The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
> >full lean.
> >
> >The carb if manually set up has 'say' 5 turns on the mix screws from
> >full rich to full lean.
> >
> >With a perfectly working system, either the stepper or the mix screws if
> >a manual BBD operate approximately in the middle of the range or at 2.5
> >turns out for the screws or jumping from step 2 to step 3 to get the O2
> >sensor to read correctly with the computer.
> >
> >Now we toss in a partially plugged idle tube or something else gummed up
> >forcing a lean to 'some' extent.
> >
> >If I am manually setting the mix, I then need to open the mix screws to
> >'say' 3 1/4 turns out to get it stable.
> >
> >In comes the stepper motor on the computer BBD. It has a choice of
> >either the 3rd step or the 4th step.
> >
> >It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
> >tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
> >
> >It keeps jumping back and forth between step 3 and 4. Every time it
> >hits step 4, it goes rich, a lot more rich than it goes lean when on
> >step 3.
> >
> >Bingo, a carb that 'just' fails emissions by being slightly rich.
>
> I think I see the problem here. You might be right if the system worked as you
> think.
>
> I don't know if you've ever watched an O2 sensor's output using a lab scope, but
> the scenario you just described would probably yield a fairly flat looking
> pattern, with the stepper motor switching between 2 steps, trying to find the
> middle. What you actually see is a consistent swing in voltage from about .2v
> to about .8v. That isn't because the computer can't find the middle, it's by
> design. In order to control emissions, the mixture needs to switch between
> slightly rich and slightly lean. When the computer sees the O2 voltage
> approaching .8v, it reverses the direction of the stepper motor to go lean. As
> voltage approaches .2v, it reverses again. The computer's job is to make the O2
> sensor dance.

So far so good....

The O2 does go rich lean, rich lean. The computer has ---- to do with
it, it does that when unplugged even. It is the O2 sensor that makes
the computer 'dance'. Or the stepper pins dance...

This is a compromise to get a good 'average' sampling rate fast enough
to have a stable tailpipe emissions. The stepper motor is a mechanical
device after all and can only physically move so fast. There is a D/A
converter involved here.

When we do it manually, we don't need to compromise like the computer
does because of the limited number of 'steps' on the stepper motor, we
can set it exact and pass emissions quite fine.

That above scenario is what I am saying and I stick with the thought
that the sampling rate and A/D and D/A converters in the computer with a
mechanical stepper motor on the mix will do exactly as I see it doing,
one 'slightly' rich carb due to a partially blocked tube or something as
I described.

Below you are talking about manually trying to make up for a carb defect
which is not applicable to the above scenario with a perfectly stock
carb.

All bets are off when the factory set of the mix screws has been moved.
Then we are no longer talking 'stock'. Then you either guess and get
tested to see or you have a sniffer up the pipe while 'guessing' to get
it back to factory range on the stepper or fix the carb or kill the
computer and just manually set the mix.

Mike

>
> So, if you have an idle tube that's partially plugged, and you adjust idle
> mixture screws to compensate, and go outside the stepper motor's range, yeah,
> it's gonna be too rich. If you go just a little too far with the screws, but
> still in the range of the stepper motor, it will continue to move in and out,
> but will stay closer to it's leanest position.
>
> >
> >I also believe this is one of the main reasons you see the mix screws
> >cut open. Forcing a mix change via the manual mix screws can make the
> >O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
> >was from the factory so when it samples it is an even 2 step to 3 step
> >pulse which puts the mix back into emissions range.
>
> I believe the reason you see them cut open, is because the guy hackin' on it
> doesn't know how to figure out what's really wrong with the carb. He also
> thinks that if 1/2 turn is good, 2 turns is better.
>
> >This is just fixing the symptoms, that blocked idle tube is still
> >there...
>
> Agreed.
>
> But if it's running acceptably, and your main goal is to get your Jeep to pass
> emissions, and the carb's been hacked already, and it's adjusted too rich too,
> giving each screw 1/2 turn lean ain't all that bad.
>
> I want to know where you can pass a smog test with 2% CO! :-)
>
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
> >>
> >> >I don't think the computer is that smart.
> >> >
> >> >I think when it sees a lean it can overcompensate.
> >>
> >> I hope you're kidding...
> >>
> >> The computer monitors O2 content of the exhaust. It alters the mix to achieve
> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
> >> smart.
> >>
> >> >
> >> >The OP was only slightly over on CO.
> >>
> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
> >>
> >> >
> >> >The stepper motor only has so many steps. The proper mix could be a
> >> >half a step leaner than the computer sets it.
> >>
> >> Which is why I said the mixture screws are probably too rich. If the stepper
> >> motor has reached it's lean limit, then the mixture screws are set too rich, or
> >> something else has gone wrong in the carb to cause a rich condition. The
> >> computer will not cause it to be too rich.
> >>
> >> >
> >> >Mike
> >> >
> >> >bllsht wrote:
> >> >>
> >> >> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
> >> >>
> >> >> >You are right, but blocked idle tubes can 'easily' make the mix go out
> >> >> >of the computer controlled stepper motor's pins travel range.
> >> >>
> >> >> Blocked idle tubes cause a lean condition. The computer will try to correct.
> >> >> If the mix is so lean it's out of the stepper motor's ability to correct the
> >> >> mix, it's still too lean.
> >> >>
> >> >> In the post I replied to, you said "Too rich can be caused from partially
> >> >> blocked idle tubes." That's not true.
> >> >>
> >> >> >
> >> >> >They adjust the air flow only, the mix screws are set at factory rich
> >> >> >and plugged off.
> >> >> >
> >> >>
> >> >> The idle mixture screws are set correctly when the stepper motor is moving in
> >> >> and out near the middle of it's range.
> >> >>
> >> >> >When the tubes really crap out, you have to remove the spring from the
> >> >> >idle speed screw in order to get any idle at all. It goes out of
> >> >> >range....
> >> >>
> >> >> That's because it's so lean you have to open the throttle to keep it running.
> >> >>
> >> >> >
> >> >> >When I see a carb with the idle speed screw compressed tight, I
> >> >> >immediately suspect partially blocked idle tubes.
> >> >> >
> >> >>
> >> >> Yes, because it's too lean and they're trying to keep it running.
> >> >>
> >> >> >Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
> >> >> >and the spring is compressed or about 3/8" long.
> >> >> >
> >> >> >If you can get at the mix screws, you can force the carb lean with
> >> >> >them, That can pass emissions usually but doesn't address why it is
> >> >> >running rich, just the symptoms.
> >> >>
> >> >> There aren't many Jeeps with carbs running around that still have sealed mixture
> >> >> screws. By now they've all been cut, drilled or whatever. It's probably too
> >> >> rich because somebody's been f*ing with it and don't know what they're doing.
> >> >>
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >bllsht wrote:
> >> >> >>
> >> >> >> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
> >> >> >>
> >> >> >> >Too rich can be caused from partially blocked idle tubes. The computer
> >> >> >> >will set the stepper motor rich.
> >> >> >>
> >> >> >> It doesn't work that way. The computer will correct the mixture (lean or rich)
> >> >> >> to achieve the "proper" amount of O2 in the exhaust.
> >> >> >>
> >> >> >> >
> >> >> >> >See this link:
> >> >> >> >
> >> >> >> >http://www.off-road.com/jeep/tech/engine/carter.html
> >> >> >> >
> >> >> >> >A bad charcoal canister can also cause that, but with a bad canister,
> >> >> >> >the idle will 'usually' surge up and down a little and you will get
> >> >> >> >spits of oil coming into the air filter from the valve cover vent.
> >> >> >> >
> >> >> >> >Mike
> >> >> >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> >> >> >> >88 Cherokee 235 BFG AT's
> >> >> >> >
> >> >> >> >bllsht wrote:
> >> >> >> >>
> >> >> >> >> High CO = too rich. Lean out the idle mixture a bit. You didn't fail by much,
> >> >> >> >> so it shouldn't take a big adjustment.
> >> >> >> >>
> >> >> >> >> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
> >> >> >> >>
> >> >> >> >> >'85 C7 258 - computer in the loop - stock everything
> >> >> >> >> >Damnit. I should have know better than to take my Jeep in for testing on a
> >> >> >> >> >rainy day but I did it anyway (it's a bit sluggish in wet weather). So here
> >> >> >> >> >are my results:
> >> >> >> >> >
> >> >> >> >> >HC PPM Idle - 223/300 -- Pass
> >> >> >> >> >HC PPM 2500 RPM - 103/300 -- Pass
> >> >> >> >> >CO % idle - 2.10/2.00 -- fail
> >> >> >> >> >CO % 2500 RPM - 1.58/2.00 -- pass
> >> >> >> >> >
> >> >> >> >> >I barely failed CO at idle -- seems all my idle readings are much higher by
> >> >> >> >> >ratio. I have been doing mostly city driving for a couple months. Would an
> >> >> >> >> >hour or so on the highway take care of the high CO? Any other hints? I
> >> >> >> >> >replaced the EGR and O2 sensor about 3000 miles ago.

 

In message <3F33D8A3.665C7744@sympatico.ca>, "Mike Romain" wrote:

>bllsht wrote:
>>
>> In message <3F327D03.CA7F4D39@sympatico.ca>, "Mike Romain" wrote:
>>
>> >Not kidding, really....
>> >
>> >Here is how I see it working. If I am mistaken, I would appreciate the
>> >feedback.
>> >
>> >The OP stated he has a 'stock everything' 85.
>> >
>> >I therefore do not assume that the carb has been drilled or cut up to
>> >access the idle mix screws.
>>
>> Well, I took 'stock everything' to mean that it had all the 'stock' equipment on
>> it. If he had said it had never been f'd with, then I might have thought the
>> plugs *may* be there, but still wouldn't expect it.
>>
>> >
>> >The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
>> >full lean.
>> >
>> >The carb if manually set up has 'say' 5 turns on the mix screws from
>> >full rich to full lean.
>> >
>> >With a perfectly working system, either the stepper or the mix screws if
>> >a manual BBD operate approximately in the middle of the range or at 2.5
>> >turns out for the screws or jumping from step 2 to step 3 to get the O2
>> >sensor to read correctly with the computer.
>> >
>> >Now we toss in a partially plugged idle tube or something else gummed up
>> >forcing a lean to 'some' extent.
>> >
>> >If I am manually setting the mix, I then need to open the mix screws to
>> >'say' 3 1/4 turns out to get it stable.
>> >
>> >In comes the stepper motor on the computer BBD. It has a choice of
>> >either the 3rd step or the 4th step.
>> >
>> >It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
>> >tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
>> >
>> >It keeps jumping back and forth between step 3 and 4. Every time it
>> >hits step 4, it goes rich, a lot more rich than it goes lean when on
>> >step 3.
>> >
>> >Bingo, a carb that 'just' fails emissions by being slightly rich.
>>
>> I think I see the problem here. You might be right if the system worked as you
>> think.
>>
>> I don't know if you've ever watched an O2 sensor's output using a lab scope, but
>> the scenario you just described would probably yield a fairly flat looking
>> pattern, with the stepper motor switching between 2 steps, trying to find the
>> middle. What you actually see is a consistent swing in voltage from about .2v
>> to about .8v. That isn't because the computer can't find the middle, it's by
>> design. In order to control emissions, the mixture needs to switch between
>> slightly rich and slightly lean. When the computer sees the O2 voltage
>> approaching .8v, it reverses the direction of the stepper motor to go lean. As
>> voltage approaches .2v, it reverses again. The computer's job is to make the O2
>> sensor dance.
>
>So far so good....
>
>The O2 does go rich lean, rich lean. The computer has ---- to do with
>it, it does that when unplugged even. It is the O2 sensor that makes
>the computer 'dance'. Or the stepper pins dance...

Wrong. The O2 sensor is a tool that the computer uses to monitor mixture
changes. The stepper motor is the tool the computer uses to change mixture.
The computer changes mixture via the stepper motor and looks at O2 sensor input
to see the results. The O2 sensor isn't a smart device. It's the computer that
runs the show.

Your thinking is just like most untrained people think, but it's wrong.

>
>This is a compromise to get a good 'average' sampling rate fast enough
>to have a stable tailpipe emissions. The stepper motor is a mechanical
>device after all and can only physically move so fast. There is a D/A
>converter involved here.

Whether there is a D/A converter involved or not isn't relevant when you're
discussing who's running the show.

On new fuel injected vehicles, you still see the O2 sensor switching from rich
to lean, and there is no mechanical device involved in changing mixture. It's
done by changing the length of time the injector is open. The computer changes
the mixture that way because that's what it has been programmed to do.

>When we do it manually, we don't need to compromise like the computer
>does because of the limited number of 'steps' on the stepper motor, we
>can set it exact and pass emissions quite fine.

If you could set it exact, there would be no need for a computer. The manual
setup is the compromise. It doesn't change with conditions, and you don't get
the correct lean/rich switching needed for tighter emission control.

>That above scenario is what I am saying and I stick with the thought
>that the sampling rate and A/D and D/A converters in the computer with a
>mechanical stepper motor on the mix will do exactly as I see it doing,
>one 'slightly' rich carb due to a partially blocked tube or something as
>I described.

And you're still wrong.

>Below you are talking about manually trying to make up for a carb defect
>which is not applicable to the above scenario with a perfectly stock
>carb.
>
>All bets are off when the factory set of the mix screws has been moved.
>Then we are no longer talking 'stock'. Then you either guess and get
>tested to see or you have a sniffer up the pipe while 'guessing' to get
>it back to factory range on the stepper or fix the carb or kill the
>computer and just manually set the mix.

If the factory setup was perfect, and should never be moved, why do you think
they would put adjustable mixture screws in? The idea of sealing the mixture
screws was to keep somebody who didn't know what they were doing from screwing
it up. If they were never meant to be moved, it would have been a lot better if
they weren't adjustable, don't ya think? They knew that in the real world,
adjustments would be necessary. There is no guessing about getting the
adjustment where it belongs. In fact, it's a simple procedure, and you don't
use a sniffer to do it.

Don't feel bad. A lot of folks don't get it.


>
>Mike
>
>>
>> So, if you have an idle tube that's partially plugged, and you adjust idle
>> mixture screws to compensate, and go outside the stepper motor's range, yeah,
>> it's gonna be too rich. If you go just a little too far with the screws, but
>> still in the range of the stepper motor, it will continue to move in and out,
>> but will stay closer to it's leanest position.
>>
>> >
>> >I also believe this is one of the main reasons you see the mix screws
>> >cut open. Forcing a mix change via the manual mix screws can make the
>> >O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
>> >was from the factory so when it samples it is an even 2 step to 3 step
>> >pulse which puts the mix back into emissions range.
>>
>> I believe the reason you see them cut open, is because the guy hackin' on it
>> doesn't know how to figure out what's really wrong with the carb. He also
>> thinks that if 1/2 turn is good, 2 turns is better.
>>
>> >This is just fixing the symptoms, that blocked idle tube is still
>> >there...
>>
>> Agreed.
>>
>> But if it's running acceptably, and your main goal is to get your Jeep to pass
>> emissions, and the carb's been hacked already, and it's adjusted too rich too,
>> giving each screw 1/2 turn lean ain't all that bad.
>>
>> I want to know where you can pass a smog test with 2% CO! :-)
>>
>> >
>> >Mike
>> >
>> >bllsht wrote:
>> >>
>> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
>> >>
>> >> >I don't think the computer is that smart.
>> >> >
>> >> >I think when it sees a lean it can overcompensate.
>> >>
>> >> I hope you're kidding...
>> >>
>> >> The computer monitors O2 content of the exhaust. It alters the mix to achieve
>> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
>> >> smart.
>> >>
>> >> >
>> >> >The OP was only slightly over on CO.
>> >>
>> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
>> >>
>> >> >
>> >> >The stepper motor only has so many steps. The proper mix could be a
>> >> >half a step leaner than the computer sets it.
>> >>
>> >> Which is why I said the mixture screws are probably too rich. If the stepper
>> >> motor has reached it's lean limit, then the mixture screws are set too rich, or
>> >> something else has gone wrong in the carb to cause a rich condition. The
>> >> computer will not cause it to be too rich.
>> >>
>> >> >
>> >> >Mike
>> >> >
>> >> >bllsht wrote:
>> >> >>
>> >> >> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
>> >> >>
>> >> >> >You are right, but blocked idle tubes can 'easily' make the mix go out
>> >> >> >of the computer controlled stepper motor's pins travel range.
>> >> >>
>> >> >> Blocked idle tubes cause a lean condition. The computer will try to correct.
>> >> >> If the mix is so lean it's out of the stepper motor's ability to correct the
>> >> >> mix, it's still too lean.
>> >> >>
>> >> >> In the post I replied to, you said "Too rich can be caused from partially
>> >> >> blocked idle tubes." That's not true.
>> >> >>
>> >> >> >
>> >> >> >They adjust the air flow only, the mix screws are set at factory rich
>> >> >> >and plugged off.
>> >> >> >
>> >> >>
>> >> >> The idle mixture screws are set correctly when the stepper motor is moving in
>> >> >> and out near the middle of it's range.
>> >> >>
>> >> >> >When the tubes really crap out, you have to remove the spring from the
>> >> >> >idle speed screw in order to get any idle at all. It goes out of
>> >> >> >range....
>> >> >>
>> >> >> That's because it's so lean you have to open the throttle to keep it running.
>> >> >>
>> >> >> >
>> >> >> >When I see a carb with the idle speed screw compressed tight, I
>> >> >> >immediately suspect partially blocked idle tubes.
>> >> >> >
>> >> >>
>> >> >> Yes, because it's too lean and they're trying to keep it running.
>> >> >>
>> >> >> >Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
>> >> >> >and the spring is compressed or about 3/8" long.
>> >> >> >
>> >> >> >If you can get at the mix screws, you can force the carb lean with
>> >> >> >them, That can pass emissions usually but doesn't address why it is
>> >> >> >running rich, just the symptoms.
>> >> >>
>> >> >> There aren't many Jeeps with carbs running around that still have sealed mixture
>> >> >> screws. By now they've all been cut, drilled or whatever. It's probably too
>> >> >> rich because somebody's been f*ing with it and don't know what they're doing.
>> >> >>
>> >> >> >
>> >> >> >Mike
>> >> >> >
>> >> >> >bllsht wrote:
>> >> >> >>
>> >> >> >> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
>> >> >> >>
>> >> >> >> >Too rich can be caused from partially blocked idle tubes. The computer
>> >> >> >> >will set the stepper motor rich.
>> >> >> >>
>> >> >> >> It doesn't work that way. The computer will correct the mixture (lean or rich)
>> >> >> >> to achieve the "proper" amount of O2 in the exhaust.
>> >> >> >>
>> >> >> >> >
>> >> >> >> >See this link:
>> >> >> >> >
>> >> >> >> >http://www.off-road.com/jeep/tech/engine/carter.html
>> >> >> >> >
>> >> >> >> >A bad charcoal canister can also cause that, but with a bad canister,
>> >> >> >> >the idle will 'usually' surge up and down a little and you will get
>> >> >> >> >spits of oil coming into the air filter from the valve cover vent.
>> >> >> >> >
>> >> >> >> >Mike
>> >> >> >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> >> >> >> >88 Cherokee 235 BFG AT's
>> >> >> >> >
>> >> >> >> >bllsht wrote:
>> >> >> >> >>
>> >> >> >> >> High CO = too rich. Lean out the idle mixture a bit. You didn't fail by much,
>> >> >> >> >> so it shouldn't take a big adjustment.
>> >> >> >> >>
>> >> >> >> >> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
>> >> >> >> >>
>> >> >> >> >> >'85 C7 258 - computer in the loop - stock everything
>> >> >> >> >> >Damnit. I should have know better than to take my Jeep in for testing on a
>> >> >> >> >> >rainy day but I did it anyway (it's a bit sluggish in wet weather). So here
>> >> >> >> >> >are my results:
>> >> >> >> >> >
>> >> >> >> >> >HC PPM Idle - 223/300 -- Pass
>> >> >> >> >> >HC PPM 2500 RPM - 103/300 -- Pass
>> >> >> >> >> >CO % idle - 2.10/2.00 -- fail
>> >> >> >> >> >CO % 2500 RPM - 1.58/2.00 -- pass
>> >> >> >> >> >
>> >> >> >> >> >I barely failed CO at idle -- seems all my idle readings are much higher by
>> >> >> >> >> >ratio. I have been doing mostly city driving for a couple months. Would an
>> >> >> >> >> >hour or so on the highway take care of the high CO? Any other hints? I
>> >> >> >> >> >replaced the EGR and O2 sensor about 3000 miles ago.

 

Well sir, I give up.

You just want to talk in circles and still haven't addressed my original
scenario which I say is 100% correct.

All you want to do is cut open a stock carb to mess with it once it is
broke.

That was not in my original premise on how a mechanically operated
although computer controlled carb can be slightly rich with a slightly
blocked idle tube.

I have a real one track mind here guy, and tossing bllsht at me ain't
about to change it.

Now if you knew what the computer sampling rate of all the sensors it
needs to read before changing anything was and the A/D input lag as well
as the D/A output lag and maybe what the maximum speed of a stepper
motor change was then maybe you could convince me that the computer can
compensate for a mix that 'needs' to be at 3.25 turns or 'steps' out
because of a blocked tube instead of the even 2.5 turns or an even 2-3
step pulse it was factory set at.

Mike

bllsht wrote:
>
> In message <3F33D8A3.665C7744@sympatico.ca>, "Mike Romain" wrote:
>
> >bllsht wrote:
> >>
> >> In message <3F327D03.CA7F4D39@sympatico.ca>, "Mike Romain" wrote:
> >>
> >> >Not kidding, really....
> >> >
> >> >Here is how I see it working. If I am mistaken, I would appreciate the
> >> >feedback.
> >> >
> >> >The OP stated he has a 'stock everything' 85.
> >> >
> >> >I therefore do not assume that the carb has been drilled or cut up to
> >> >access the idle mix screws.
> >>
> >> Well, I took 'stock everything' to mean that it had all the 'stock' equipment on
> >> it. If he had said it had never been f'd with, then I might have thought the
> >> plugs *may* be there, but still wouldn't expect it.
> >>
> >> >
> >> >The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
> >> >full lean.
> >> >
> >> >The carb if manually set up has 'say' 5 turns on the mix screws from
> >> >full rich to full lean.
> >> >
> >> >With a perfectly working system, either the stepper or the mix screws if
> >> >a manual BBD operate approximately in the middle of the range or at 2.5
> >> >turns out for the screws or jumping from step 2 to step 3 to get the O2
> >> >sensor to read correctly with the computer.
> >> >
> >> >Now we toss in a partially plugged idle tube or something else gummed up
> >> >forcing a lean to 'some' extent.
> >> >
> >> >If I am manually setting the mix, I then need to open the mix screws to
> >> >'say' 3 1/4 turns out to get it stable.
> >> >
> >> >In comes the stepper motor on the computer BBD. It has a choice of
> >> >either the 3rd step or the 4th step.
> >> >
> >> >It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
> >> >tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
> >> >
> >> >It keeps jumping back and forth between step 3 and 4. Every time it
> >> >hits step 4, it goes rich, a lot more rich than it goes lean when on
> >> >step 3.
> >> >
> >> >Bingo, a carb that 'just' fails emissions by being slightly rich.
> >>
> >> I think I see the problem here. You might be right if the system worked as you
> >> think.
> >>
> >> I don't know if you've ever watched an O2 sensor's output using a lab scope, but
> >> the scenario you just described would probably yield a fairly flat looking
> >> pattern, with the stepper motor switching between 2 steps, trying to find the
> >> middle. What you actually see is a consistent swing in voltage from about .2v
> >> to about .8v. That isn't because the computer can't find the middle, it's by
> >> design. In order to control emissions, the mixture needs to switch between
> >> slightly rich and slightly lean. When the computer sees the O2 voltage
> >> approaching .8v, it reverses the direction of the stepper motor to go lean. As
> >> voltage approaches .2v, it reverses again. The computer's job is to make the O2
> >> sensor dance.
> >
> >So far so good....
> >
> >The O2 does go rich lean, rich lean. The computer has ---- to do with
> >it, it does that when unplugged even. It is the O2 sensor that makes
> >the computer 'dance'. Or the stepper pins dance...
>
> Wrong. The O2 sensor is a tool that the computer uses to monitor mixture
> changes. The stepper motor is the tool the computer uses to change mixture.
> The computer changes mixture via the stepper motor and looks at O2 sensor input
> to see the results. The O2 sensor isn't a smart device. It's the computer that
> runs the show.
>
> Your thinking is just like most untrained people think, but it's wrong.
>
> >
> >This is a compromise to get a good 'average' sampling rate fast enough
> >to have a stable tailpipe emissions. The stepper motor is a mechanical
> >device after all and can only physically move so fast. There is a D/A
> >converter involved here.
>
> Whether there is a D/A converter involved or not isn't relevant when you're
> discussing who's running the show.
>
> On new fuel injected vehicles, you still see the O2 sensor switching from rich
> to lean, and there is no mechanical device involved in changing mixture. It's
> done by changing the length of time the injector is open. The computer changes
> the mixture that way because that's what it has been programmed to do.
>
> >When we do it manually, we don't need to compromise like the computer
> >does because of the limited number of 'steps' on the stepper motor, we
> >can set it exact and pass emissions quite fine.
>
> If you could set it exact, there would be no need for a computer. The manual
> setup is the compromise. It doesn't change with conditions, and you don't get
> the correct lean/rich switching needed for tighter emission control.
>
> >That above scenario is what I am saying and I stick with the thought
> >that the sampling rate and A/D and D/A converters in the computer with a
> >mechanical stepper motor on the mix will do exactly as I see it doing,
> >one 'slightly' rich carb due to a partially blocked tube or something as
> >I described.
>
> And you're still wrong.
>
> >Below you are talking about manually trying to make up for a carb defect
> >which is not applicable to the above scenario with a perfectly stock
> >carb.
> >
> >All bets are off when the factory set of the mix screws has been moved.
> >Then we are no longer talking 'stock'. Then you either guess and get
> >tested to see or you have a sniffer up the pipe while 'guessing' to get
> >it back to factory range on the stepper or fix the carb or kill the
> >computer and just manually set the mix.
>
> If the factory setup was perfect, and should never be moved, why do you think
> they would put adjustable mixture screws in? The idea of sealing the mixture
> screws was to keep somebody who didn't know what they were doing from screwing
> it up. If they were never meant to be moved, it would have been a lot better if
> they weren't adjustable, don't ya think? They knew that in the real world,
> adjustments would be necessary. There is no guessing about getting the
> adjustment where it belongs. In fact, it's a simple procedure, and you don't
> use a sniffer to do it.
>
> Don't feel bad. A lot of folks don't get it.
>
> >
> >Mike
> >
> >>
> >> So, if you have an idle tube that's partially plugged, and you adjust idle
> >> mixture screws to compensate, and go outside the stepper motor's range, yeah,
> >> it's gonna be too rich. If you go just a little too far with the screws, but
> >> still in the range of the stepper motor, it will continue to move in and out,
> >> but will stay closer to it's leanest position.
> >>
> >> >
> >> >I also believe this is one of the main reasons you see the mix screws
> >> >cut open. Forcing a mix change via the manual mix screws can make the
> >> >O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
> >> >was from the factory so when it samples it is an even 2 step to 3 step
> >> >pulse which puts the mix back into emissions range.
> >>
> >> I believe the reason you see them cut open, is because the guy hackin' on it
> >> doesn't know how to figure out what's really wrong with the carb. He also
> >> thinks that if 1/2 turn is good, 2 turns is better.
> >>
> >> >This is just fixing the symptoms, that blocked idle tube is still
> >> >there...
> >>
> >> Agreed.
> >>
> >> But if it's running acceptably, and your main goal is to get your Jeep to pass
> >> emissions, and the carb's been hacked already, and it's adjusted too rich too,
> >> giving each screw 1/2 turn lean ain't all that bad.
> >>
> >> I want to know where you can pass a smog test with 2% CO! :-)
> >>
> >> >
> >> >Mike
> >> >
> >> >bllsht wrote:
> >> >>
> >> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
> >> >>
> >> >> >I don't think the computer is that smart.
> >> >> >
> >> >> >I think when it sees a lean it can overcompensate.
> >> >>
> >> >> I hope you're kidding...
> >> >>
> >> >> The computer monitors O2 content of the exhaust. It alters the mix to achieve
> >> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
> >> >> smart.
> >> >>
> >> >> >
> >> >> >The OP was only slightly over on CO.
> >> >>
> >> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
> >> >>
> >> >> >
> >> >> >The stepper motor only has so many steps. The proper mix could be a
> >> >> >half a step leaner than the computer sets it.
> >> >>
> >> >> Which is why I said the mixture screws are probably too rich. If the stepper
> >> >> motor has reached it's lean limit, then the mixture screws are set too rich, or
> >> >> something else has gone wrong in the carb to cause a rich condition. The
> >> >> computer will not cause it to be too rich.
> >> >>
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >bllsht wrote:
> >> >> >>
> >> >> >> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
> >> >> >>
> >> >> >> >You are right, but blocked idle tubes can 'easily' make the mix go out
> >> >> >> >of the computer controlled stepper motor's pins travel range.
> >> >> >>
> >> >> >> Blocked idle tubes cause a lean condition. The computer will try to correct.
> >> >> >> If the mix is so lean it's out of the stepper motor's ability to correct the
> >> >> >> mix, it's still too lean.
> >> >> >>
> >> >> >> In the post I replied to, you said "Too rich can be caused from partially
> >> >> >> blocked idle tubes." That's not true.
> >> >> >>
> >> >> >> >
> >> >> >> >They adjust the air flow only, the mix screws are set at factory rich
> >> >> >> >and plugged off.
> >> >> >> >
> >> >> >>
> >> >> >> The idle mixture screws are set correctly when the stepper motor is moving in
> >> >> >> and out near the middle of it's range.
> >> >> >>
> >> >> >> >When the tubes really crap out, you have to remove the spring from the
> >> >> >> >idle speed screw in order to get any idle at all. It goes out of
> >> >> >> >range....
> >> >> >>
> >> >> >> That's because it's so lean you have to open the throttle to keep it running.
> >> >> >>
> >> >> >> >
> >> >> >> >When I see a carb with the idle speed screw compressed tight, I
> >> >> >> >immediately suspect partially blocked idle tubes.
> >> >> >> >
> >> >> >>
> >> >> >> Yes, because it's too lean and they're trying to keep it running.
> >> >> >>
> >> >> >> >Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
> >> >> >> >and the spring is compressed or about 3/8" long.
> >> >> >> >
> >> >> >> >If you can get at the mix screws, you can force the carb lean with
> >> >> >> >them, That can pass emissions usually but doesn't address why it is
> >> >> >> >running rich, just the symptoms.
> >> >> >>
> >> >> >> There aren't many Jeeps with carbs running around that still have sealed mixture
> >> >> >> screws. By now they've all been cut, drilled or whatever. It's probably too
> >> >> >> rich because somebody's been f*ing with it and don't know what they're doing.
> >> >> >>
> >> >> >> >
> >> >> >> >Mike
> >> >> >> >
> >> >> >> >bllsht wrote:
> >> >> >> >>
> >> >> >> >> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
> >> >> >> >>
> >> >> >> >> >Too rich can be caused from partially blocked idle tubes. The computer
> >> >> >> >> >will set the stepper motor rich.
> >> >> >> >>
> >> >> >> >> It doesn't work that way. The computer will correct the mixture (lean or rich)
> >> >> >> >> to achieve the "proper" amount of O2 in the exhaust.
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >See this link:
> >> >> >> >> >
> >> >> >> >> >http://www.off-road.com/jeep/tech/engine/carter.html
> >> >> >> >> >
> >> >> >> >> >A bad charcoal canister can also cause that, but with a bad canister,
> >> >> >> >> >the idle will 'usually' surge up and down a little and you will get
> >> >> >> >> >spits of oil coming into the air filter from the valve cover vent.
> >> >> >> >> >
> >> >> >> >> >Mike
> >> >> >> >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> >> >> >> >> >88 Cherokee 235 BFG AT's
> >> >> >> >> >
> >> >> >> >> >bllsht wrote:
> >> >> >> >> >>
> >> >> >> >> >> High CO = too rich. Lean out the idle mixture a bit. You didn't fail by much,
> >> >> >> >> >> so it shouldn't take a big adjustment.
> >> >> >> >> >>
> >> >> >> >> >> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
> >> >> >> >> >>
> >> >> >> >> >> >'85 C7 258 - computer in the loop - stock everything
> >> >> >> >> >> >Damnit. I should have know better than to take my Jeep in for testing on a
> >> >> >> >> >> >rainy day but I did it anyway (it's a bit sluggish in wet weather). So here
> >> >> >> >> >> >are my results:
> >> >> >> >> >> >
> >> >> >> >> >> >HC PPM Idle - 223/300 -- Pass
> >> >> >> >> >> >HC PPM 2500 RPM - 103/300 -- Pass
> >> >> >> >> >> >CO % idle - 2.10/2.00 -- fail
> >> >> >> >> >> >CO % 2500 RPM - 1.58/2.00 -- pass
> >> >> >> >> >> >
> >> >> >> >> >> >I barely failed CO at idle -- seems all my idle readings are much higher by
> >> >> >> >> >> >ratio. I have been doing mostly city driving for a couple months. Would an
> >> >> >> >> >> >hour or so on the highway take care of the high CO? Any other hints? I
> >> >> >> >> >> >replaced the EGR and O2 sensor about 3000 miles ago.

 

LOL!

You have no clue how the computer does it's 'thing' and just 'why' the
factory setting has to have the mix match the D/A timing pulse of the
stepper pins do you?

Mike


bllsht wrote:
>
> In message <3F35042A.8F57320C@sympatico.ca>, "Mike Romain" wrote:
>
> >Well sir, I give up.
>
> Oh, that was too easy! I couldn't help but notice that you didn't address
> anything in my last post.
> >
> >You just want to talk in circles and still haven't addressed my original
> >scenario which I say is 100% correct.
>
> I addressed your original theory. It's wrong, and I told you why. Repeating 'I
> am right' doesn't make it so.
>
> >
> >All you want to do is cut open a stock carb to mess with it once it is
> >broke.
>
> I get it now. English is a 2nd language for you, isn't it? Kindly quote where
> I said that.
>
> You have this idea that there's a 'magic' setting that only the factory can get
> to. It's just not true. If it were true, they'd tell you to set the mixture
> screws at '3.1275' turns out. What they actually tell you is to have the
> stepper motor operating in the middle of it's range, and the computer will
> handle it from there, because it can, and I've told you how.
>
> >
> >That was not in my original premise on how a mechanically operated
> >although computer controlled carb can be slightly rich with a slightly
> >blocked idle tube.
>
> Your premise depends on your theory about what the computer does.
> Unfortunately, your theory has no impact on reality. What you 'think' or 'wish'
> don't change what 'is'.
>
> >
> >I have a real one track mind here guy, and tossing bllsht at me ain't
> >about to change it.
>
> Yes, I'm aware that facts take a back seat to your desire to be right.
>
> >
> >Now if you knew what the computer sampling rate of all the sensors it
> >needs to read before changing anything was and the A/D input lag as well
> >as the D/A output lag and maybe what the maximum speed of a stepper
> >motor change was then maybe you could convince me that the computer can
> >compensate for a mix that 'needs' to be at 3.25 turns or 'steps' out
> >because of a blocked tube instead of the even 2.5 turns or an even 2-3
> >step pulse it was factory set at.
>
> Smoke screen. The computer was put in to control fuel mixture and compensate
> for changing conditions. That's what it does.
>
> >
> >Mike
> >
> >bllsht wrote:
> >>
> >> In message <3F33D8A3.665C7744@sympatico.ca>, "Mike Romain" wrote:
> >>
> >> >bllsht wrote:
> >> >>
> >> >> In message <3F327D03.CA7F4D39@sympatico.ca>, "Mike Romain" wrote:
> >> >>
> >> >> >Not kidding, really....
> >> >> >
> >> >> >Here is how I see it working. If I am mistaken, I would appreciate the
> >> >> >feedback.
> >> >> >
> >> >> >The OP stated he has a 'stock everything' 85.
> >> >> >
> >> >> >I therefore do not assume that the carb has been drilled or cut up to
> >> >> >access the idle mix screws.
> >> >>
> >> >> Well, I took 'stock everything' to mean that it had all the 'stock' equipment on
> >> >> it. If he had said it had never been f'd with, then I might have thought the
> >> >> plugs *may* be there, but still wouldn't expect it.
> >> >>
> >> >> >
> >> >> >The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
> >> >> >full lean.
> >> >> >
> >> >> >The carb if manually set up has 'say' 5 turns on the mix screws from
> >> >> >full rich to full lean.
> >> >> >
> >> >> >With a perfectly working system, either the stepper or the mix screws if
> >> >> >a manual BBD operate approximately in the middle of the range or at 2.5
> >> >> >turns out for the screws or jumping from step 2 to step 3 to get the O2
> >> >> >sensor to read correctly with the computer.
> >> >> >
> >> >> >Now we toss in a partially plugged idle tube or something else gummed up
> >> >> >forcing a lean to 'some' extent.
> >> >> >
> >> >> >If I am manually setting the mix, I then need to open the mix screws to
> >> >> >'say' 3 1/4 turns out to get it stable.
> >> >> >
> >> >> >In comes the stepper motor on the computer BBD. It has a choice of
> >> >> >either the 3rd step or the 4th step.
> >> >> >
> >> >> >It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
> >> >> >tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
> >> >> >
> >> >> >It keeps jumping back and forth between step 3 and 4. Every time it
> >> >> >hits step 4, it goes rich, a lot more rich than it goes lean when on
> >> >> >step 3.
> >> >> >
> >> >> >Bingo, a carb that 'just' fails emissions by being slightly rich.
> >> >>
> >> >> I think I see the problem here. You might be right if the system worked as you
> >> >> think.
> >> >>
> >> >> I don't know if you've ever watched an O2 sensor's output using a lab scope, but
> >> >> the scenario you just described would probably yield a fairly flat looking
> >> >> pattern, with the stepper motor switching between 2 steps, trying to find the
> >> >> middle. What you actually see is a consistent swing in voltage from about .2v
> >> >> to about .8v. That isn't because the computer can't find the middle, it's by
> >> >> design. In order to control emissions, the mixture needs to switch between
> >> >> slightly rich and slightly lean. When the computer sees the O2 voltage
> >> >> approaching .8v, it reverses the direction of the stepper motor to go lean. As
> >> >> voltage approaches .2v, it reverses again. The computer's job is to make the O2
> >> >> sensor dance.
> >> >
> >> >So far so good....
> >> >
> >> >The O2 does go rich lean, rich lean. The computer has ---- to do with
> >> >it, it does that when unplugged even. It is the O2 sensor that makes
> >> >the computer 'dance'. Or the stepper pins dance...
> >>
> >> Wrong. The O2 sensor is a tool that the computer uses to monitor mixture
> >> changes. The stepper motor is the tool the computer uses to change mixture.
> >> The computer changes mixture via the stepper motor and looks at O2 sensor input
> >> to see the results. The O2 sensor isn't a smart device. It's the computer that
> >> runs the show.
> >>
> >> Your thinking is just like most untrained people think, but it's wrong.
> >>
> >> >
> >> >This is a compromise to get a good 'average' sampling rate fast enough
> >> >to have a stable tailpipe emissions. The stepper motor is a mechanical
> >> >device after all and can only physically move so fast. There is a D/A
> >> >converter involved here.
> >>
> >> Whether there is a D/A converter involved or not isn't relevant when you're
> >> discussing who's running the show.
> >>
> >> On new fuel injected vehicles, you still see the O2 sensor switching from rich
> >> to lean, and there is no mechanical device involved in changing mixture. It's
> >> done by changing the length of time the injector is open. The computer changes
> >> the mixture that way because that's what it has been programmed to do.
> >>
> >> >When we do it manually, we don't need to compromise like the computer
> >> >does because of the limited number of 'steps' on the stepper motor, we
> >> >can set it exact and pass emissions quite fine.
> >>
> >> If you could set it exact, there would be no need for a computer. The manual
> >> setup is the compromise. It doesn't change with conditions, and you don't get
> >> the correct lean/rich switching needed for tighter emission control.
> >>
> >> >That above scenario is what I am saying and I stick with the thought
> >> >that the sampling rate and A/D and D/A converters in the computer with a
> >> >mechanical stepper motor on the mix will do exactly as I see it doing,
> >> >one 'slightly' rich carb due to a partially blocked tube or something as
> >> >I described.
> >>
> >> And you're still wrong.
> >>
> >> >Below you are talking about manually trying to make up for a carb defect
> >> >which is not applicable to the above scenario with a perfectly stock
> >> >carb.
> >> >
> >> >All bets are off when the factory set of the mix screws has been moved.
> >> >Then we are no longer talking 'stock'. Then you either guess and get
> >> >tested to see or you have a sniffer up the pipe while 'guessing' to get
> >> >it back to factory range on the stepper or fix the carb or kill the
> >> >computer and just manually set the mix.
> >>
> >> If the factory setup was perfect, and should never be moved, why do you think
> >> they would put adjustable mixture screws in? The idea of sealing the mixture
> >> screws was to keep somebody who didn't know what they were doing from screwing
> >> it up. If they were never meant to be moved, it would have been a lot better if
> >> they weren't adjustable, don't ya think? They knew that in the real world,
> >> adjustments would be necessary. There is no guessing about getting the
> >> adjustment where it belongs. In fact, it's a simple procedure, and you don't
> >> use a sniffer to do it.
> >>
> >> Don't feel bad. A lot of folks don't get it.
> >>
> >> >
> >> >Mike
> >> >
> >> >>
> >> >> So, if you have an idle tube that's partially plugged, and you adjust idle
> >> >> mixture screws to compensate, and go outside the stepper motor's range, yeah,
> >> >> it's gonna be too rich. If you go just a little too far with the screws, but
> >> >> still in the range of the stepper motor, it will continue to move in and out,
> >> >> but will stay closer to it's leanest position.
> >> >>
> >> >> >
> >> >> >I also believe this is one of the main reasons you see the mix screws
> >> >> >cut open. Forcing a mix change via the manual mix screws can make the
> >> >> >O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
> >> >> >was from the factory so when it samples it is an even 2 step to 3 step
> >> >> >pulse which puts the mix back into emissions range.
> >> >>
> >> >> I believe the reason you see them cut open, is because the guy hackin' on it
> >> >> doesn't know how to figure out what's really wrong with the carb. He also
> >> >> thinks that if 1/2 turn is good, 2 turns is better.
> >> >>
> >> >> >This is just fixing the symptoms, that blocked idle tube is still
> >> >> >there...
> >> >>
> >> >> Agreed.
> >> >>
> >> >> But if it's running acceptably, and your main goal is to get your Jeep to pass
> >> >> emissions, and the carb's been hacked already, and it's adjusted too rich too,
> >> >> giving each screw 1/2 turn lean ain't all that bad.
> >> >>
> >> >> I want to know where you can pass a smog test with 2% CO! :-)
> >> >>
> >> >> >
> >> >> >Mike
> >> >> >
> >> >> >bllsht wrote:
> >> >> >>
> >> >> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
> >> >> >>
> >> >> >> >I don't think the computer is that smart.
> >> >> >> >
> >> >> >> >I think when it sees a lean it can overcompensate.
> >> >> >>
> >> >> >> I hope you're kidding...
> >> >> >>
> >> >> >> The computer monitors O2 content of the exhaust. It alters the mix to achieve
> >> >> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
> >> >> >> smart.
> >> >> >>
> >> >> >> >
> >> >> >> >The OP was only slightly over on CO.
> >> >> >>
> >> >> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
> >> >> >>
> >> >> >> >
> >> >> >> >The stepper motor only has so many steps. The proper mix could be a
> >> >> >> >half a step leaner than the computer sets it.
> >> >> >>
> >> >> >> Which is why I said the mixture screws are probably too rich. If the stepper
> >> >> >> motor has reached it's lean limit, then the mixture screws are set too rich, or
> >> >> >> something else has gone wrong in the carb to cause a rich condition. The
> >> >> >> computer will not cause it to be too rich.
> >> >> >>
> >> >> >> >
> >> >> >> >Mike
> >> >> >> >
> >> >> >> >bllsht wrote:
> >> >> >> >>
> >> >> >> >> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
> >> >> >> >>
> >> >> >> >> >You are right, but blocked idle tubes can 'easily' make the mix go out
> >> >> >> >> >of the computer controlled stepper motor's pins travel range.
> >> >> >> >>
> >> >> >> >> Blocked idle tubes cause a lean condition. The computer will try to correct.
> >> >> >> >> If the mix is so lean it's out of the stepper motor's ability to correct the
> >> >> >> >> mix, it's still too lean.
> >> >> >> >>
> >> >> >> >> In the post I replied to, you said "Too rich can be caused from partially
> >> >> >> >> blocked idle tubes." That's not true.
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >They adjust the air flow only, the mix screws are set at factory rich
> >> >> >> >> >and plugged off.
> >> >> >> >> >
> >> >> >> >>
> >> >> >> >> The idle mixture screws are set correctly when the stepper motor is moving in
> >> >> >> >> and out near the middle of it's range.
> >> >> >> >>
> >> >> >> >> >When the tubes really crap out, you have to remove the spring from the
> >> >> >> >> >idle speed screw in order to get any idle at all. It goes out of
> >> >> >> >> >range....
> >> >> >> >>
> >> >> >> >> That's because it's so lean you have to open the throttle to keep it running.
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >When I see a carb with the idle speed screw compressed tight, I
> >> >> >> >> >immediately suspect partially blocked idle tubes.
> >> >> >> >> >
> >> >> >> >>
> >> >> >> >> Yes, because it's too lean and they're trying to keep it running.
> >> >> >> >>
> >> >> >> >> >Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
> >> >> >> >> >and the spring is compressed or about 3/8" long.
> >> >> >> >> >
> >> >> >> >> >If you can get at the mix screws, you can force the carb lean with
> >> >> >> >> >them, That can pass emissions usually but doesn't address why it is
> >> >> >> >> >running rich, just the symptoms.
> >> >> >> >>
> >> >> >> >> There aren't many Jeeps with carbs running around that still have sealed mixture
> >> >> >> >> screws. By now they've all been cut, drilled or whatever. It's probably too
> >> >> >> >> rich because somebody's been f*ing with it and don't know what they're doing.
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >Mike
> >> >> >> >> >
> >> >> >> >> >bllsht wrote:
> >> >> >> >> >>
> >> >> >> >> >> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
> >> >> >> >> >>
> >> >> >> >> >> >Too rich can be caused from partially blocked idle tubes. The computer
> >> >> >> >> >> >will set the stepper motor rich.
> >> >> >> >> >>
> >> >> >> >> >> It doesn't work that way. The computer will correct the mixture (lean or rich)
> >> >> >> >> >> to achieve the "proper" amount of O2 in the exhaust.
> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >> >See this link:
> >> >> >> >> >> >
> >> >> >> >> >> >http://www.off-road.com/jeep/tech/engine/carter.html
> >> >> >> >> >> >
> >> >> >> >> >> >A bad charcoal canister can also cause that, but with a bad canister,
> >> >> >> >> >> >the idle will 'usually' surge up and down a little and you will get
> >> >> >> >> >> >spits of oil coming into the air filter from the valve cover vent.
> >> >> >> >> >> >
> >> >> >> >> >> >Mike
> >> >> >> >> >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> >> >> >> >> >> >88 Cherokee 235 BFG AT's
> >> >> >> >> >> >
> >> >> >> >> >> >bllsht wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> High CO = too rich. Lean out the idle mixture a bit. You didn't fail by much,
> >> >> >> >> >> >> so it shouldn't take a big adjustment.
> >> >> >> >> >> >>
> >> >> >> >> >> >> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> >'85 C7 258 - computer in the loop - stock everything
> >> >> >> >> >> >> >Damnit. I should have know better than to take my Jeep in for testing on a
> >> >> >> >> >> >> >rainy day but I did it anyway (it's a bit sluggish in wet weather). So here
> >> >> >> >> >> >> >are my results:
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >HC PPM Idle - 223/300 -- Pass
> >> >> >> >> >> >> >HC PPM 2500 RPM - 103/300 -- Pass
> >> >> >> >> >> >> >CO % idle - 2.10/2.00 -- fail
> >> >> >> >> >> >> >CO % 2500 RPM - 1.58/2.00 -- pass
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >I barely failed CO at idle -- seems all my idle readings are much higher by
> >> >> >> >> >> >> >ratio. I have been doing mostly city driving for a couple months. Would an
> >> >> >> >> >> >> >hour or so on the highway take care of the high CO? Any other hints? I
> >> >> >> >> >> >> >replaced the EGR and O2 sensor about 3000 miles ago.

 

So tell me. When you adjusted your idle mixture, how did you match the mix to
the D/A timing pulses?

Oh, you didn't?

Why not?

Don't they give you that info in the service manual?

Why not?

Why is it important for the factory settings to match this, but not adjustments
made in the field?

If they should never be moved, why are they adjustable anyway?

Why does the factory service manual give you the procedure to remove the plugs,
and adjust the mixture, but mentions nothing about D/A timing pulses?

There's also adjustments for the main metering circuit, and they don't mention
D/A pulse timing either. Doesn't it need to match at higher rpm also?

Why is that stuff adjustable?

This should be good.

You're just throwing out BS now, to dazzle those who don't know any better.

In message <3F3549A7.B2362A1A@sympatico.ca>, "Mike Romain" wrote:

>LOL!
>
>You have no clue how the computer does it's 'thing' and just 'why' the
>factory setting has to have the mix match the D/A timing pulse of the
>stepper pins do you?
>
>Mike
>
>
>bllsht wrote:
>>
>> In message <3F35042A.8F57320C@sympatico.ca>, "Mike Romain" wrote:
>>
>> >Well sir, I give up.
>>
>> Oh, that was too easy! I couldn't help but notice that you didn't address
>> anything in my last post.
>> >
>> >You just want to talk in circles and still haven't addressed my original
>> >scenario which I say is 100% correct.
>>
>> I addressed your original theory. It's wrong, and I told you why. Repeating 'I
>> am right' doesn't make it so.
>>
>> >
>> >All you want to do is cut open a stock carb to mess with it once it is
>> >broke.
>>
>> I get it now. English is a 2nd language for you, isn't it? Kindly quote where
>> I said that.
>>
>> You have this idea that there's a 'magic' setting that only the factory can get
>> to. It's just not true. If it were true, they'd tell you to set the mixture
>> screws at '3.1275' turns out. What they actually tell you is to have the
>> stepper motor operating in the middle of it's range, and the computer will
>> handle it from there, because it can, and I've told you how.
>>
>> >
>> >That was not in my original premise on how a mechanically operated
>> >although computer controlled carb can be slightly rich with a slightly
>> >blocked idle tube.
>>
>> Your premise depends on your theory about what the computer does.
>> Unfortunately, your theory has no impact on reality. What you 'think' or 'wish'
>> don't change what 'is'.
>>
>> >
>> >I have a real one track mind here guy, and tossing bllsht at me ain't
>> >about to change it.
>>
>> Yes, I'm aware that facts take a back seat to your desire to be right.
>>
>> >
>> >Now if you knew what the computer sampling rate of all the sensors it
>> >needs to read before changing anything was and the A/D input lag as well
>> >as the D/A output lag and maybe what the maximum speed of a stepper
>> >motor change was then maybe you could convince me that the computer can
>> >compensate for a mix that 'needs' to be at 3.25 turns or 'steps' out
>> >because of a blocked tube instead of the even 2.5 turns or an even 2-3
>> >step pulse it was factory set at.
>>
>> Smoke screen. The computer was put in to control fuel mixture and compensate
>> for changing conditions. That's what it does.
>>
>> >
>> >Mike
>> >
>> >bllsht wrote:
>> >>
>> >> In message <3F33D8A3.665C7744@sympatico.ca>, "Mike Romain" wrote:
>> >>
>> >> >bllsht wrote:
>> >> >>
>> >> >> In message <3F327D03.CA7F4D39@sympatico.ca>, "Mike Romain" wrote:
>> >> >>
>> >> >> >Not kidding, really....
>> >> >> >
>> >> >> >Here is how I see it working. If I am mistaken, I would appreciate the
>> >> >> >feedback.
>> >> >> >
>> >> >> >The OP stated he has a 'stock everything' 85.
>> >> >> >
>> >> >> >I therefore do not assume that the carb has been drilled or cut up to
>> >> >> >access the idle mix screws.
>> >> >>
>> >> >> Well, I took 'stock everything' to mean that it had all the 'stock' equipment on
>> >> >> it. If he had said it had never been f'd with, then I might have thought the
>> >> >> plugs *may* be there, but still wouldn't expect it.
>> >> >>
>> >> >> >
>> >> >> >The stepper motor has (for easy numbers) 'say' 5 steps from full rich to
>> >> >> >full lean.
>> >> >> >
>> >> >> >The carb if manually set up has 'say' 5 turns on the mix screws from
>> >> >> >full rich to full lean.
>> >> >> >
>> >> >> >With a perfectly working system, either the stepper or the mix screws if
>> >> >> >a manual BBD operate approximately in the middle of the range or at 2.5
>> >> >> >turns out for the screws or jumping from step 2 to step 3 to get the O2
>> >> >> >sensor to read correctly with the computer.
>> >> >> >
>> >> >> >Now we toss in a partially plugged idle tube or something else gummed up
>> >> >> >forcing a lean to 'some' extent.
>> >> >> >
>> >> >> >If I am manually setting the mix, I then need to open the mix screws to
>> >> >> >'say' 3 1/4 turns out to get it stable.
>> >> >> >
>> >> >> >In comes the stepper motor on the computer BBD. It has a choice of
>> >> >> >either the 3rd step or the 4th step.
>> >> >> >
>> >> >> >It tries step 3, nope, too lean. 1/4 turn too lean if manual. It then
>> >> >> >tries step 4, nope again, too rich. 3/4 a turn if manual too rich.
>> >> >> >
>> >> >> >It keeps jumping back and forth between step 3 and 4. Every time it
>> >> >> >hits step 4, it goes rich, a lot more rich than it goes lean when on
>> >> >> >step 3.
>> >> >> >
>> >> >> >Bingo, a carb that 'just' fails emissions by being slightly rich.
>> >> >>
>> >> >> I think I see the problem here. You might be right if the system worked as you
>> >> >> think.
>> >> >>
>> >> >> I don't know if you've ever watched an O2 sensor's output using a lab scope, but
>> >> >> the scenario you just described would probably yield a fairly flat looking
>> >> >> pattern, with the stepper motor switching between 2 steps, trying to find the
>> >> >> middle. What you actually see is a consistent swing in voltage from about .2v
>> >> >> to about .8v. That isn't because the computer can't find the middle, it's by
>> >> >> design. In order to control emissions, the mixture needs to switch between
>> >> >> slightly rich and slightly lean. When the computer sees the O2 voltage
>> >> >> approaching .8v, it reverses the direction of the stepper motor to go lean. As
>> >> >> voltage approaches .2v, it reverses again. The computer's job is to make the O2
>> >> >> sensor dance.
>> >> >
>> >> >So far so good....
>> >> >
>> >> >The O2 does go rich lean, rich lean. The computer has ---- to do with
>> >> >it, it does that when unplugged even. It is the O2 sensor that makes
>> >> >the computer 'dance'. Or the stepper pins dance...
>> >>
>> >> Wrong. The O2 sensor is a tool that the computer uses to monitor mixture
>> >> changes. The stepper motor is the tool the computer uses to change mixture.
>> >> The computer changes mixture via the stepper motor and looks at O2 sensor input
>> >> to see the results. The O2 sensor isn't a smart device. It's the computer that
>> >> runs the show.
>> >>
>> >> Your thinking is just like most untrained people think, but it's wrong.
>> >>
>> >> >
>> >> >This is a compromise to get a good 'average' sampling rate fast enough
>> >> >to have a stable tailpipe emissions. The stepper motor is a mechanical
>> >> >device after all and can only physically move so fast. There is a D/A
>> >> >converter involved here.
>> >>
>> >> Whether there is a D/A converter involved or not isn't relevant when you're
>> >> discussing who's running the show.
>> >>
>> >> On new fuel injected vehicles, you still see the O2 sensor switching from rich
>> >> to lean, and there is no mechanical device involved in changing mixture. It's
>> >> done by changing the length of time the injector is open. The computer changes
>> >> the mixture that way because that's what it has been programmed to do.
>> >>
>> >> >When we do it manually, we don't need to compromise like the computer
>> >> >does because of the limited number of 'steps' on the stepper motor, we
>> >> >can set it exact and pass emissions quite fine.
>> >>
>> >> If you could set it exact, there would be no need for a computer. The manual
>> >> setup is the compromise. It doesn't change with conditions, and you don't get
>> >> the correct lean/rich switching needed for tighter emission control.
>> >>
>> >> >That above scenario is what I am saying and I stick with the thought
>> >> >that the sampling rate and A/D and D/A converters in the computer with a
>> >> >mechanical stepper motor on the mix will do exactly as I see it doing,
>> >> >one 'slightly' rich carb due to a partially blocked tube or something as
>> >> >I described.
>> >>
>> >> And you're still wrong.
>> >>
>> >> >Below you are talking about manually trying to make up for a carb defect
>> >> >which is not applicable to the above scenario with a perfectly stock
>> >> >carb.
>> >> >
>> >> >All bets are off when the factory set of the mix screws has been moved.
>> >> >Then we are no longer talking 'stock'. Then you either guess and get
>> >> >tested to see or you have a sniffer up the pipe while 'guessing' to get
>> >> >it back to factory range on the stepper or fix the carb or kill the
>> >> >computer and just manually set the mix.
>> >>
>> >> If the factory setup was perfect, and should never be moved, why do you think
>> >> they would put adjustable mixture screws in? The idea of sealing the mixture
>> >> screws was to keep somebody who didn't know what they were doing from screwing
>> >> it up. If they were never meant to be moved, it would have been a lot better if
>> >> they weren't adjustable, don't ya think? They knew that in the real world,
>> >> adjustments would be necessary. There is no guessing about getting the
>> >> adjustment where it belongs. In fact, it's a simple procedure, and you don't
>> >> use a sniffer to do it.
>> >>
>> >> Don't feel bad. A lot of folks don't get it.
>> >>
>> >> >
>> >> >Mike
>> >> >
>> >> >>
>> >> >> So, if you have an idle tube that's partially plugged, and you adjust idle
>> >> >> mixture screws to compensate, and go outside the stepper motor's range, yeah,
>> >> >> it's gonna be too rich. If you go just a little too far with the screws, but
>> >> >> still in the range of the stepper motor, it will continue to move in and out,
>> >> >> but will stay closer to it's leanest position.
>> >> >>
>> >> >> >
>> >> >> >I also believe this is one of the main reasons you see the mix screws
>> >> >> >cut open. Forcing a mix change via the manual mix screws can make the
>> >> >> >O2 tell the stepper motor to 'see' it as 'say' 2.5 steps exact like it
>> >> >> >was from the factory so when it samples it is an even 2 step to 3 step
>> >> >> >pulse which puts the mix back into emissions range.
>> >> >>
>> >> >> I believe the reason you see them cut open, is because the guy hackin' on it
>> >> >> doesn't know how to figure out what's really wrong with the carb. He also
>> >> >> thinks that if 1/2 turn is good, 2 turns is better.
>> >> >>
>> >> >> >This is just fixing the symptoms, that blocked idle tube is still
>> >> >> >there...
>> >> >>
>> >> >> Agreed.
>> >> >>
>> >> >> But if it's running acceptably, and your main goal is to get your Jeep to pass
>> >> >> emissions, and the carb's been hacked already, and it's adjusted too rich too,
>> >> >> giving each screw 1/2 turn lean ain't all that bad.
>> >> >>
>> >> >> I want to know where you can pass a smog test with 2% CO! :-)
>> >> >>
>> >> >> >
>> >> >> >Mike
>> >> >> >
>> >> >> >bllsht wrote:
>> >> >> >>
>> >> >> >> In message <3F315E76.96E87105@sympatico.ca>, "Mike Romain" wrote:
>> >> >> >>
>> >> >> >> >I don't think the computer is that smart.
>> >> >> >> >
>> >> >> >> >I think when it sees a lean it can overcompensate.
>> >> >> >>
>> >> >> >> I hope you're kidding...
>> >> >> >>
>> >> >> >> The computer monitors O2 content of the exhaust. It alters the mix to achieve
>> >> >> >> it's desired O2 level. That's what it's designed to do, and yes, it is that
>> >> >> >> smart.
>> >> >> >>
>> >> >> >> >
>> >> >> >> >The OP was only slightly over on CO.
>> >> >> >>
>> >> >> >> Right. Too rich. Too much fuel. Not enough O2. That's what I said.
>> >> >> >>
>> >> >> >> >
>> >> >> >> >The stepper motor only has so many steps. The proper mix could be a
>> >> >> >> >half a step leaner than the computer sets it.
>> >> >> >>
>> >> >> >> Which is why I said the mixture screws are probably too rich. If the stepper
>> >> >> >> motor has reached it's lean limit, then the mixture screws are set too rich, or
>> >> >> >> something else has gone wrong in the carb to cause a rich condition. The
>> >> >> >> computer will not cause it to be too rich.
>> >> >> >>
>> >> >> >> >
>> >> >> >> >Mike
>> >> >> >> >
>> >> >> >> >bllsht wrote:
>> >> >> >> >>
>> >> >> >> >> In message <3F308C26.20BCB15@sympatico.ca>, "Mike Romain" wrote:
>> >> >> >> >>
>> >> >> >> >> >You are right, but blocked idle tubes can 'easily' make the mix go out
>> >> >> >> >> >of the computer controlled stepper motor's pins travel range.
>> >> >> >> >>
>> >> >> >> >> Blocked idle tubes cause a lean condition. The computer will try to correct.
>> >> >> >> >> If the mix is so lean it's out of the stepper motor's ability to correct the
>> >> >> >> >> mix, it's still too lean.
>> >> >> >> >>
>> >> >> >> >> In the post I replied to, you said "Too rich can be caused from partially
>> >> >> >> >> blocked idle tubes." That's not true.
>> >> >> >> >>
>> >> >> >> >> >
>> >> >> >> >> >They adjust the air flow only, the mix screws are set at factory rich
>> >> >> >> >> >and plugged off.
>> >> >> >> >> >
>> >> >> >> >>
>> >> >> >> >> The idle mixture screws are set correctly when the stepper motor is moving in
>> >> >> >> >> and out near the middle of it's range.
>> >> >> >> >>
>> >> >> >> >> >When the tubes really crap out, you have to remove the spring from the
>> >> >> >> >> >idle speed screw in order to get any idle at all. It goes out of
>> >> >> >> >> >range....
>> >> >> >> >>
>> >> >> >> >> That's because it's so lean you have to open the throttle to keep it running.
>> >> >> >> >>
>> >> >> >> >> >
>> >> >> >> >> >When I see a carb with the idle speed screw compressed tight, I
>> >> >> >> >> >immediately suspect partially blocked idle tubes.
>> >> >> >> >> >
>> >> >> >> >>
>> >> >> >> >> Yes, because it's too lean and they're trying to keep it running.
>> >> >> >> >>
>> >> >> >> >> >Clean tubes and the mix screw spring is about 5/8" long, plugged tubes
>> >> >> >> >> >and the spring is compressed or about 3/8" long.
>> >> >> >> >> >
>> >> >> >> >> >If you can get at the mix screws, you can force the carb lean with
>> >> >> >> >> >them, That can pass emissions usually but doesn't address why it is
>> >> >> >> >> >running rich, just the symptoms.
>> >> >> >> >>
>> >> >> >> >> There aren't many Jeeps with carbs running around that still have sealed mixture
>> >> >> >> >> screws. By now they've all been cut, drilled or whatever. It's probably too
>> >> >> >> >> rich because somebody's been f*ing with it and don't know what they're doing.
>> >> >> >> >>
>> >> >> >> >> >
>> >> >> >> >> >Mike
>> >> >> >> >> >
>> >> >> >> >> >bllsht wrote:
>> >> >> >> >> >>
>> >> >> >> >> >> In message <3F2FD37B.CE04B6CC@sympatico.ca>, "Mike Romain" wrote:
>> >> >> >> >> >>
>> >> >> >> >> >> >Too rich can be caused from partially blocked idle tubes. The computer
>> >> >> >> >> >> >will set the stepper motor rich.
>> >> >> >> >> >>
>> >> >> >> >> >> It doesn't work that way. The computer will correct the mixture (lean or rich)
>> >> >> >> >> >> to achieve the "proper" amount of O2 in the exhaust.
>> >> >> >> >> >>
>> >> >> >> >> >> >
>> >> >> >> >> >> >See this link:
>> >> >> >> >> >> >
>> >> >> >> >> >> >http://www.off-road.com/jeep/tech/engine/carter.html
>> >> >> >> >> >> >
>> >> >> >> >> >> >A bad charcoal canister can also cause that, but with a bad canister,
>> >> >> >> >> >> >the idle will 'usually' surge up and down a little and you will get
>> >> >> >> >> >> >spits of oil coming into the air filter from the valve cover vent.
>> >> >> >> >> >> >
>> >> >> >> >> >> >Mike
>> >> >> >> >> >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> >> >> >> >> >> >88 Cherokee 235 BFG AT's
>> >> >> >> >> >> >
>> >> >> >> >> >> >bllsht wrote:
>> >> >> >> >> >> >>
>> >> >> >> >> >> >> High CO = too rich. Lean out the idle mixture a bit. You didn't fail by much,
>> >> >> >> >> >> >> so it shouldn't take a big adjustment.
>> >> >> >> >> >> >>
>> >> >> >> >> >> >> In message <BB542759.1BE22%nospam@thanksImFull.spam>, "KurtS" wrote:
>> >> >> >> >> >> >>
>> >> >> >> >> >> >> >'85 C7 258 - computer in the loop - stock everything
>> >> >> >> >> >> >> >Damnit. I should have know better than to take my Jeep in for testing on a
>> >> >> >> >> >> >> >rainy day but I did it anyway (it's a bit sluggish in wet weather). So here
>> >> >> >> >> >> >> >are my results:
>> >> >> >> >> >> >> >
>> >> >> >> >> >> >> >HC PPM Idle - 223/300 -- Pass
>> >> >> >> >> >> >> >HC PPM 2500 RPM - 103/300 -- Pass
>> >> >> >> >> >> >> >CO % idle - 2.10/2.00 -- fail
>> >> >> >> >> >> >> >CO % 2500 RPM - 1.58/2.00 -- pass
>> >> >> >> >> >> >> >
>> >> >> >> >> >> >> >I barely failed CO at idle -- seems all my idle readings are much higher by
>> >> >> >> >> >> >> >ratio. I have been doing mostly city driving for a couple months. Would an
>> >> >> >> >> >> >> >hour or so on the highway take care of the high CO? Any other hints? I
>> >> >> >> >> >> >> >replaced the EGR and O2 sensor about 3000 miles ago.

 

On Sun, 10 Aug 2003 12:13:21 -0400 in rec.autos.makers.jeep+******,
Mike Romain <romainm@sympatico.ca> wrote:

>There is 'NO' idle mix adjustment on a stock Carter BBD with a stepper
>motor!

Actually, that's not true. For documentation, please refer to the
Jeep TSB I am posting separately under the subject:
"BBD Carburetor - Idle Mixture Adjustment TSB"

 

David Harmon wrote:
>
> On Sun, 10 Aug 2003 12:13:21 -0400 in rec.autos.makers.jeep+******,
> Mike Romain <romainm@sympatico.ca> wrote:
>
> >There is 'NO' idle mix adjustment on a stock Carter BBD with a stepper
> >motor!
>
> Actually, that's not true. For documentation, please refer to the
> Jeep TSB I am posting separately under the subject:
> "BBD Carburetor - Idle Mixture Adjustment TSB"

Well, still true.

You still have to cut the carb open to set it. A 'stock' carb has the
mix screws blocked from the factory.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

 

In message <3f49639d.102019177@news.west.earthlink.net>, "David Harmon" wrote:

>On Sun, 10 Aug 2003 12:13:21 -0400 in rec.autos.makers.jeep+******,
>Mike Romain <romainm@sympatico.ca> wrote:
>
>>There is 'NO' idle mix adjustment on a stock Carter BBD with a stepper
>>motor!
>
>Actually, that's not true. For documentation, please refer to the
>Jeep TSB I am posting separately under the subject:
>"BBD Carburetor - Idle Mixture Adjustment TSB"

I guess you've noticed by now that facts mean nothing to Mike.

 

In message <3F37A546.1738D3A8@sympatico.ca>, "Mike Romain" wrote:

>David Harmon wrote:
>>
>> On Sun, 10 Aug 2003 12:13:21 -0400 in rec.autos.makers.jeep+******,
>> Mike Romain <romainm@sympatico.ca> wrote:
>>
>> >There is 'NO' idle mix adjustment on a stock Carter BBD with a stepper
>> >motor!
>>
>> Actually, that's not true. For documentation, please refer to the
>> Jeep TSB I am posting separately under the subject:
>> "BBD Carburetor - Idle Mixture Adjustment TSB"
>
>Well, still true.
>
>You still have to cut the carb open to set it. A 'stock' carb has the
>mix screws blocked from the factory.

That's like saying that once you adjust your brakes, they are no longer 'stock'.

Give it up.


>
>Mike
>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>88 Cherokee 235 BFG AT's