On Tue, 16 Sep 2003 02:54:35 UTC "Homer Simpson" <me@privacy.net>
wrote:

> thx for the insights....my new IAC doesn't make a difference...grrrrr....I
> hate guesswork mechanics! I will look at the MAP and ground strap and then
> off it will go to my mechanic. He is a great guy and often he will diagnose
> things for me and tell me how to fix it so I can learn.
>
> This issue has gotten to the point of me becoming stubborn and wanting to
> figure it out myself!
>
> Stay tuned...

Enjoy! I spent nearly 6 months after I bought the MJ dicking with the
idle/off idle stuff. Like the Johnny Cash song "One Piece at a Time",
I finally got it to idle and run smooth just off idle. Seemed like
everything I did helped to some degree but there was always just a
little more to do. I think that the last step for me was to replace
the O2 sensor but I had replaced or tested everything else by then.

--
Will Honea <whonea@codenet.net>

 

The dealer told me on one of the 88 XJs I work on, it is usually the TPS.
Sure enough I changed the TPS and the idle went to normal and both the used
and new ISS motor worked fine.
later,
dave

"Homer Simpson" <me@privacy.net> wrote in message
news:bk5u5o$phvkk$1@ID-185934.news.uni-berlin.de...
>
> "Will Honea" <whonea@codenet.net> wrote in message
> news:JxX2tWiP5BNp-pn2-f3vssGC5e2rw@anon.none.net...
> >
> > Now you've illuminated something: that stepper pulls a significant
> > current when it pulses and the stumble sounds like a MAP sensor. How
> > about a bad ground for the computer/sensor grounds? Hit the IAC and
> > screw up the other sensor readings with a shifting ground???
> >
> > Just for grins, check the engine to firewall strap on both ends as
> > well as the ground point inside up above the accelerator pedal.
>
> thx for the insights....my new IAC doesn't make a difference...grrrrr....I
> hate guesswork mechanics! I will look at the MAP and ground strap and then
> off it will go to my mechanic. He is a great guy and often he will
diagnose
> things for me and tell me how to fix it so I can learn.
>
> This issue has gotten to the point of me becoming stubborn and wanting to
> figure it out myself!
>
> Stay tuned...
>
>

 

The dealer told me on one of the 88 XJs I work on, it is usually the TPS.
Sure enough I changed the TPS and the idle went to normal and both the used
and new ISS motor worked fine.
later,
dave

"Homer Simpson" <me@privacy.net> wrote in message
news:bk5u5o$phvkk$1@ID-185934.news.uni-berlin.de...
>
> "Will Honea" <whonea@codenet.net> wrote in message
> news:JxX2tWiP5BNp-pn2-f3vssGC5e2rw@anon.none.net...
> >
> > Now you've illuminated something: that stepper pulls a significant
> > current when it pulses and the stumble sounds like a MAP sensor. How
> > about a bad ground for the computer/sensor grounds? Hit the IAC and
> > screw up the other sensor readings with a shifting ground???
> >
> > Just for grins, check the engine to firewall strap on both ends as
> > well as the ground point inside up above the accelerator pedal.
>
> thx for the insights....my new IAC doesn't make a difference...grrrrr....I
> hate guesswork mechanics! I will look at the MAP and ground strap and then
> off it will go to my mechanic. He is a great guy and often he will
diagnose
> things for me and tell me how to fix it so I can learn.
>
> This issue has gotten to the point of me becoming stubborn and wanting to
> figure it out myself!
>
> Stay tuned...
>
>

 

IIRC
the ISS motor will be affected/adjusted/moved by info from the TPS and the
ECM along with other sensors.
AFAIK the TPS is usually the main problem.
Here is a little info on the TPS;
http://members.tripod.com/BillyXJ/SENSORS1/page1.html
later,
dave

"Jelly" <formatccolon@yahoo.com> wrote in message
news:6da21666.0309210307.4c862de4@posting.google.c om...
> "Will Honea" <whonea@codenet.net> wrote in message
news:<JxX2tWiP5BNp-pn2-MDEU3DvqQbt6@anon.none.net>...
> > On Fri, 12 Sep 2003 02:53:21 UTC "Homer Simpson" <me@privacy.net>
> > wrote:
> >
> > >
> > > "Will Honea" <whonea@codenet.net> wrote in message
> > > news:JxX2tWiP5BNp-pn2-DSoq6Nqd9o4R@anon.none.net...
> > > >> Damn, that sounds expensive for the IAC motor! I think I gave $25
or
> > > > $30 for mine when I swapped it out a couple of years ago (got it
from
> > > > Advanced Auto).
> > >
> > > Well I am in Canada and thinsg are expensive up here!
> > >
> > > Today was no better and I am still having the same problem after
cleaning up
> > > the stepper motor....
> > >
> > > I wonder what would happen if the stepper motor was engaged on a hot
engine
> > > and I pressed the accelerator, would it stumble?
> > >
> > > If so it would help diagnose the source. But if it did stumble when
the
> > > stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> > > me if power is removed, it comes back in, and is not stuck.
> > >
> > > So confused! I at least have enough info to take it to my reputable
> > > mechanic.....
> > >
> > > My O2 sensor is fine so I guess I can look at the MAP aspects of it.
Funny
> > > my Factory manual for my CJ was awesome for diags, but the XJ sucks
> > > beans.....
> > >
> > > If I don't figure it out it will go into the shop as it is now a daily
> > > occurance &^$#*#^$
> >
> > The IAC motor is in fact a stepper motor - uses phased excitation of
> > the coils to rotate it - and it's gonna stay where it was when you
> > pulled power off. I don't have the exact one handy at the moment, but
> > on similar GM models you could depress the spring on the shaft to
> > clear a locking ridge and manually twist the thing to set it. One of
> > the precedures when changing those was to move it in far enough to
> > prevent jamming it when you installed it. I think (but don't hold me
> > to it) that you can do the same with the Jeep IAC. Just don't force
> > it and break something! I'm going from memory here and a bunch of
> > other steppers I've used in other applications, but you should be able
> > to measure the resistance between pairs of pins or to ground to check
> > for opens. Some motors reverse the polarity as well as the sequence
> > in which they energize the coils to control direction, others use a
> > grounded coil and just control the sequence.
> >
> > The stepper moves the pointed end in and out of the hole it fits into
> > about like adjusting an idle jet screw on an old carb - except the
> > effect is to control the amount of air passing and not fuel. It isn't
> > instantaneous but it's reasonably fast acting. The only way I know of
> > to really test one without the proper control module is to unplug it
> > and adjust it manually until it just closes off the port. Start the
> > engine - you'll probably need to play with the accelerator to get it
> > going - then open it one turn, try again until the engine idles
> > smoothly at 800 RPM. Now try accelerating fairly slowly - should not
> > stumble unless you punch it.
> >
> > It took me almost 6 months to get my 88 MJ to idle right. I wound up
> > pulling the throttle body and soaking it out in carb cleaner,
> > replacing the IAC, the MAP sensor, and finally the O2 sensor. The
> > cleaning did a lot of good, the MAP helped accleration (hesitation)
> > all across the range, a new IAC stabilized the idle speed, and the O2
> > sensor got the idle smooth without dying at stop signs - finally - but
> > it was a battle!
>
>
> BAD JEEP IDLE ( start engine, and it runs real fast idle)
> Given: CPS is good OK !
> 4.0 Liter , I-6 engine , fuel injected with IAC throttle body.
>
> I am adding this information because this was the best posting on this
> subject.
> Very good.! IAC.
> The pentil of the IAC set the proper EPA idle , under any load ( ac no
> ac, etc)
> This pentil cone face is INFAMOUS for gumming up.
> Even when the car was new ( I have 3 Jeep XJ's).
>
> Here is the fix .
> Low cost , lasts a long time. 40 to 50k miles , before needed again.
> ( my first thought was to teflon coat the cone , but... )
>
> To shorten the story here goes.
> go to your favorite gun store. ( fancy Sportco is one good one)
> At the gun lub section , see Gun Action DRY lub. in a spray can.
> It is also called Moly lub and other names.
> You spary just the cone. Put back the iAC and you are good to go.
>
> This dry lub looks like dried Teflon, as it is real slippery and will
> not rub off.
> where gloves to put it on or your wife will gripe.
> Get those nasty hands off me, hah !
>
> I have done this over 10 times in 16 years on all my jeeps and it is a
> god send.
>
> Newer jeeps have a more powerful IAC so ,this is not your cure.
>
> The cause is PCV fumes backing up the intake and gumming up the IAC
> port.
> Make sure PCV is venting good , but like I said , this happens on new
> Jeeps made back in
> 1988 until , unknown, date.
>
> Good luck one and all, and good day.
>
> Jelly the Gear Head.
>
> posdmr-xxx@yahoo.com (remove -xxx)

 

IIRC
the ISS motor will be affected/adjusted/moved by info from the TPS and the
ECM along with other sensors.
AFAIK the TPS is usually the main problem.
Here is a little info on the TPS;
http://members.tripod.com/BillyXJ/SENSORS1/page1.html
later,
dave

"Jelly" <formatccolon@yahoo.com> wrote in message
news:6da21666.0309210307.4c862de4@posting.google.c om...
> "Will Honea" <whonea@codenet.net> wrote in message
news:<JxX2tWiP5BNp-pn2-MDEU3DvqQbt6@anon.none.net>...
> > On Fri, 12 Sep 2003 02:53:21 UTC "Homer Simpson" <me@privacy.net>
> > wrote:
> >
> > >
> > > "Will Honea" <whonea@codenet.net> wrote in message
> > > news:JxX2tWiP5BNp-pn2-DSoq6Nqd9o4R@anon.none.net...
> > > >> Damn, that sounds expensive for the IAC motor! I think I gave $25
or
> > > > $30 for mine when I swapped it out a couple of years ago (got it
from
> > > > Advanced Auto).
> > >
> > > Well I am in Canada and thinsg are expensive up here!
> > >
> > > Today was no better and I am still having the same problem after
cleaning up
> > > the stepper motor....
> > >
> > > I wonder what would happen if the stepper motor was engaged on a hot
engine
> > > and I pressed the accelerator, would it stumble?
> > >
> > > If so it would help diagnose the source. But if it did stumble when
the
> > > stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> > > me if power is removed, it comes back in, and is not stuck.
> > >
> > > So confused! I at least have enough info to take it to my reputable
> > > mechanic.....
> > >
> > > My O2 sensor is fine so I guess I can look at the MAP aspects of it.
Funny
> > > my Factory manual for my CJ was awesome for diags, but the XJ sucks
> > > beans.....
> > >
> > > If I don't figure it out it will go into the shop as it is now a daily
> > > occurance &^$#*#^$
> >
> > The IAC motor is in fact a stepper motor - uses phased excitation of
> > the coils to rotate it - and it's gonna stay where it was when you
> > pulled power off. I don't have the exact one handy at the moment, but
> > on similar GM models you could depress the spring on the shaft to
> > clear a locking ridge and manually twist the thing to set it. One of
> > the precedures when changing those was to move it in far enough to
> > prevent jamming it when you installed it. I think (but don't hold me
> > to it) that you can do the same with the Jeep IAC. Just don't force
> > it and break something! I'm going from memory here and a bunch of
> > other steppers I've used in other applications, but you should be able
> > to measure the resistance between pairs of pins or to ground to check
> > for opens. Some motors reverse the polarity as well as the sequence
> > in which they energize the coils to control direction, others use a
> > grounded coil and just control the sequence.
> >
> > The stepper moves the pointed end in and out of the hole it fits into
> > about like adjusting an idle jet screw on an old carb - except the
> > effect is to control the amount of air passing and not fuel. It isn't
> > instantaneous but it's reasonably fast acting. The only way I know of
> > to really test one without the proper control module is to unplug it
> > and adjust it manually until it just closes off the port. Start the
> > engine - you'll probably need to play with the accelerator to get it
> > going - then open it one turn, try again until the engine idles
> > smoothly at 800 RPM. Now try accelerating fairly slowly - should not
> > stumble unless you punch it.
> >
> > It took me almost 6 months to get my 88 MJ to idle right. I wound up
> > pulling the throttle body and soaking it out in carb cleaner,
> > replacing the IAC, the MAP sensor, and finally the O2 sensor. The
> > cleaning did a lot of good, the MAP helped accleration (hesitation)
> > all across the range, a new IAC stabilized the idle speed, and the O2
> > sensor got the idle smooth without dying at stop signs - finally - but
> > it was a battle!
>
>
> BAD JEEP IDLE ( start engine, and it runs real fast idle)
> Given: CPS is good OK !
> 4.0 Liter , I-6 engine , fuel injected with IAC throttle body.
>
> I am adding this information because this was the best posting on this
> subject.
> Very good.! IAC.
> The pentil of the IAC set the proper EPA idle , under any load ( ac no
> ac, etc)
> This pentil cone face is INFAMOUS for gumming up.
> Even when the car was new ( I have 3 Jeep XJ's).
>
> Here is the fix .
> Low cost , lasts a long time. 40 to 50k miles , before needed again.
> ( my first thought was to teflon coat the cone , but... )
>
> To shorten the story here goes.
> go to your favorite gun store. ( fancy Sportco is one good one)
> At the gun lub section , see Gun Action DRY lub. in a spray can.
> It is also called Moly lub and other names.
> You spary just the cone. Put back the iAC and you are good to go.
>
> This dry lub looks like dried Teflon, as it is real slippery and will
> not rub off.
> where gloves to put it on or your wife will gripe.
> Get those nasty hands off me, hah !
>
> I have done this over 10 times in 16 years on all my jeeps and it is a
> god send.
>
> Newer jeeps have a more powerful IAC so ,this is not your cure.
>
> The cause is PCV fumes backing up the intake and gumming up the IAC
> port.
> Make sure PCV is venting good , but like I said , this happens on new
> Jeeps made back in
> 1988 until , unknown, date.
>
> Good luck one and all, and good day.
>
> Jelly the Gear Head.
>
> posdmr-xxx@yahoo.com (remove -xxx)