Distributor Vacuum Advance Problem
Guest
Posts: n/a
Distributor Vacuum Advance Problem
I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
I recently replaced the exhaust manifold and replaced both the intake
and exhaust manifold gaskets. I also rebuilt the carb. even though it
was working fine, figured at 19 yrs old it was time. Upon completion I
noticed the engine would shudder ( a very low grumbling/coughing type
noise) at idle and during acceleration. And no it isn't the idler
tubes. This is all happening while in neutral, and far less noticeable
when driving under load.
I first thought I had an air leak in the intake manifold, which I
might. I also thought maybe I messed up the carb. rebuild, which again
is highly possible. However, when I disconnected and plugged the
vacuum advance at the distribtor to check the timing I noticed it was
idling and running smooth and consistent under acceleration again. So
this leads me to believe this is a distributor issue.
What does that dashpot/diaphram at the base of the distributor do
anyway? Are the plugs misfiring? Am I getting too much or too little
vacuum at the distr? The distr. cap, plugs and wires are all fairly
new, several years old but only have 1000 miles or so on them. The car
also has really bad knock and ping problems. Anyone have any ideas
what is causing this, your help will be greatly appreciated.
Thanks in advance,
Kevin
I recently replaced the exhaust manifold and replaced both the intake
and exhaust manifold gaskets. I also rebuilt the carb. even though it
was working fine, figured at 19 yrs old it was time. Upon completion I
noticed the engine would shudder ( a very low grumbling/coughing type
noise) at idle and during acceleration. And no it isn't the idler
tubes. This is all happening while in neutral, and far less noticeable
when driving under load.
I first thought I had an air leak in the intake manifold, which I
might. I also thought maybe I messed up the carb. rebuild, which again
is highly possible. However, when I disconnected and plugged the
vacuum advance at the distribtor to check the timing I noticed it was
idling and running smooth and consistent under acceleration again. So
this leads me to believe this is a distributor issue.
What does that dashpot/diaphram at the base of the distributor do
anyway? Are the plugs misfiring? Am I getting too much or too little
vacuum at the distr? The distr. cap, plugs and wires are all fairly
new, several years old but only have 1000 miles or so on them. The car
also has really bad knock and ping problems. Anyone have any ideas
what is causing this, your help will be greatly appreciated.
Thanks in advance,
Kevin
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
The advance plate and sleeve need regular lubrication. To do this you
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
The advance plate and sleeve need regular lubrication. To do this you
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
The advance plate and sleeve need regular lubrication. To do this you
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
remove the rotor and soak the pad below it in the tube with 10W30 oil.
You then manually work the plate to get the oil back in it.
The pot there should hold a vacuum when you suck on it.
If the computer sees a bad sensor somewhere, it will put the timing into
'limp home mode' and it will run like a bag of dirt.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Kevin wrote:
>
> I have an 87 Wrangler 4.2L I6 258 man. trans with the Carter BBD carb.
> I recently replaced the exhaust manifold and replaced both the intake
> and exhaust manifold gaskets. I also rebuilt the carb. even though it
> was working fine, figured at 19 yrs old it was time. Upon completion I
> noticed the engine would shudder ( a very low grumbling/coughing type
> noise) at idle and during acceleration. And no it isn't the idler
> tubes. This is all happening while in neutral, and far less noticeable
> when driving under load.
>
> I first thought I had an air leak in the intake manifold, which I
> might. I also thought maybe I messed up the carb. rebuild, which again
> is highly possible. However, when I disconnected and plugged the
> vacuum advance at the distribtor to check the timing I noticed it was
> idling and running smooth and consistent under acceleration again. So
> this leads me to believe this is a distributor issue.
>
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this, your help will be greatly appreciated.
> Thanks in advance,
> Kevin
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Kevin wrote:
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Kevin wrote:
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Kevin wrote:
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
> What does that dashpot/diaphram at the base of the distributor do
> anyway? Are the plugs misfiring? Am I getting too much or too little
> vacuum at the distr? The distr. cap, plugs and wires are all fairly
> new, several years old but only have 1000 miles or so on them. The car
> also has really bad knock and ping problems. Anyone have any ideas
> what is causing this
Check for lean fuel mixture, get an air/fuel guage and tune the carb
with it.
Check for worn cam and lifters, if you find you can't advance the timing
much without knock, and it starts knocking with revs above 2k plug the
advance and run it... if you still get knock at higher RPM's; retard the
timing until it just idles smoothly (right before the retard causes
rough idle) if at that point you still can't totally eliminate the knock
when under load or revving higher than 2,000 RPM's then I'd bet on it
needing a new Cam and timing set.
I'm betting you had the same knock and ping problems before AND after
the carb rebuild and new gaskets right? Which caused you to do the work
in the first place. I bet it also starts horribly rough in winter but
much better in warmer months.
--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Air fuel gauge to tune the carb?????
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Air fuel gauge to tune the carb?????
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
Guest
Posts: n/a
Re: Distributor Vacuum Advance Problem
Air fuel gauge to tune the carb?????
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you
need a computer to tell you how to fix them you are screwed and should
not go anywhere near them.
For starts, his carb is not 'tunable', he has a computer running it.
The idle mix screws are supposed to be blocked with a plug. If it was
not put back exactly the same as before, it will run like a bag of dirt.
Now if he has the computer disabled, then it is a different story and he
should have stated this.
The computer also runs the timing and controls the advance
electronically. There is a mechanical and vacuum advance as well.
If any of the sensors have failed, it dumps the advance down for 'limp
home' mode. I suppose he could take a hammer and hit the manifold a
couple times to see if the engine stumbles. This would verify the
computer is still functioning with the knock sensor at least.
There is about a 15 degree difference in the base timing when the
computer is working and not working. With the computer in the loop, you
have to use the emissions sticker way to set the timing. I believe that
is a set at 1600 rpm with the vacuum line off so the mechanical advance
is full, not at idle like you do with no computer.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
Simon Juncal wrote:
>
> Kevin wrote:
> > What does that dashpot/diaphram at the base of the distributor do
> > anyway? Are the plugs misfiring? Am I getting too much or too little
> > vacuum at the distr? The distr. cap, plugs and wires are all fairly
> > new, several years old but only have 1000 miles or so on them. The car
> > also has really bad knock and ping problems. Anyone have any ideas
> > what is causing this
>
> Check for lean fuel mixture, get an air/fuel guage and tune the carb
> with it.
>
> Check for worn cam and lifters, if you find you can't advance the timing
> much without knock, and it starts knocking with revs above 2k plug the
> advance and run it... if you still get knock at higher RPM's; retard the
> timing until it just idles smoothly (right before the retard causes
> rough idle) if at that point you still can't totally eliminate the knock
> when under load or revving higher than 2,000 RPM's then I'd bet on it
> needing a new Cam and timing set.
>
> I'm betting you had the same knock and ping problems before AND after
> the carb rebuild and new gaskets right? Which caused you to do the work
> in the first place. I bet it also starts horribly rough in winter but
> much better in warmer months.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
