4.0 idle stepper motor
09-12-2003, 12:46 AM
#11
Guest
Posts: n/a
Re: 4.0 idle stepper motor
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!
--
Will Honea <whonea@codenet.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!
--
Will Honea <whonea@codenet.net>
09-12-2003, 12:51 AM
#12
Guest
Posts: n/a
Re: 4.0 idle stepper motor
I agree with Will... The stepper motor just controls idle speed. The only
way I can think of it causing stumble is if the idle was too low, but that
would be obvious.
Have you done all of the usual tune up items including plug wires?
Joe, 90XJ
"Homer Simpson" <me@privacy.net> wrote in message
news:bjrcj2$m7903$1@ID-185934.news.uni-berlin.de...
>
> "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
> > $30 for mine when I swapped it out a couple of years ago (got it from
> > Advanced Auto).
>
> Well I am in Canada and thinsg are expensive up here!
>
> Today was no better and I am still having the same problem after cleaning
up
> the stepper motor....
>
> I wonder what would happen if the stepper motor was engaged on a hot
engine
> and I pressed the accelerator, would it stumble?
>
> If so it would help diagnose the source. But if it did stumble when the
> stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> me if power is removed, it comes back in, and is not stuck.
>
> So confused! I at least have enough info to take it to my reputable
> mechanic.....
>
> My O2 sensor is fine so I guess I can look at the MAP aspects of it. Funny
> my Factory manual for my CJ was awesome for diags, but the XJ sucks
> beans.....
>
> If I don't figure it out it will go into the shop as it is now a daily
> occurance &^$#*#^$
>
> > Next, on the top of the throttle body there is a hole, about 1/4 inch
> > in diameter, on the fender side. That runs down to a plugged hole way
> > down on the side. Under that plug is a jet. use a knife point or ice
> > pick (remember those?) and pull the plug out. Turn the jet all the
> > way in counting the turns so that you can get it back to where it was.
> > Now, take the jet all the way out and clean that hole. It's an idle
> > air bypass and runs all the way down into the mainfold. Mine was
> > plugged solid and it took a lot of soaking and a long piano wire to
> > get it cleaned out. Put the jet back in and adjust it to where it
> > was. You can cover the access hole with silicone like the book says
> > or just forget it. Clean the contacts in the IAC plug with WD40 and a
> > stiff brush.
> >
> > The IAC opens and closes to allow more or less air to pass instead of
> > having to adjust the butterfly throttle plate t maintain an idle RPM.
> > If it fails in an appropriate position to maintain a decent cold idle
> > you see idle speed increase as the engine warms up or a high idle when
> > you come to a stop. If it fails closed then cold starts will be a
> > bitch and you will have to play with the throttle to keep it running
> > once you do get it started. It also accounts for the higher cold
> > start idle speed. I've rarely seen one cause stumbles on acceleration
> > other than on a dead cold engine. The O2 sensor is a more likely
> > candidate if it stumbles - or a plugged/bad MAP sensor. Clean the map
> > tube and hole in the throttle body as well.
> >
> > One caution: DO NOT turn the key on while the IAC is out and plugged
> > in - it throws the shaft clear accross the garage and it's hell to get
> > back together right!
> >
> > --
> > Will Honea <whonea@codenet.net>
>
>
way I can think of it causing stumble is if the idle was too low, but that
would be obvious.
Have you done all of the usual tune up items including plug wires?
Joe, 90XJ
"Homer Simpson" <me@privacy.net> wrote in message
news:bjrcj2$m7903$1@ID-185934.news.uni-berlin.de...
>
> "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
> > $30 for mine when I swapped it out a couple of years ago (got it from
> > Advanced Auto).
>
> Well I am in Canada and thinsg are expensive up here!
>
> Today was no better and I am still having the same problem after cleaning
up
> the stepper motor....
>
> I wonder what would happen if the stepper motor was engaged on a hot
engine
> and I pressed the accelerator, would it stumble?
>
> If so it would help diagnose the source. But if it did stumble when the
> stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> me if power is removed, it comes back in, and is not stuck.
>
> So confused! I at least have enough info to take it to my reputable
> mechanic.....
>
> My O2 sensor is fine so I guess I can look at the MAP aspects of it. Funny
> my Factory manual for my CJ was awesome for diags, but the XJ sucks
> beans.....
>
> If I don't figure it out it will go into the shop as it is now a daily
> occurance &^$#*#^$
>
> > Next, on the top of the throttle body there is a hole, about 1/4 inch
> > in diameter, on the fender side. That runs down to a plugged hole way
> > down on the side. Under that plug is a jet. use a knife point or ice
> > pick (remember those?) and pull the plug out. Turn the jet all the
> > way in counting the turns so that you can get it back to where it was.
> > Now, take the jet all the way out and clean that hole. It's an idle
> > air bypass and runs all the way down into the mainfold. Mine was
> > plugged solid and it took a lot of soaking and a long piano wire to
> > get it cleaned out. Put the jet back in and adjust it to where it
> > was. You can cover the access hole with silicone like the book says
> > or just forget it. Clean the contacts in the IAC plug with WD40 and a
> > stiff brush.
> >
> > The IAC opens and closes to allow more or less air to pass instead of
> > having to adjust the butterfly throttle plate t maintain an idle RPM.
> > If it fails in an appropriate position to maintain a decent cold idle
> > you see idle speed increase as the engine warms up or a high idle when
> > you come to a stop. If it fails closed then cold starts will be a
> > bitch and you will have to play with the throttle to keep it running
> > once you do get it started. It also accounts for the higher cold
> > start idle speed. I've rarely seen one cause stumbles on acceleration
> > other than on a dead cold engine. The O2 sensor is a more likely
> > candidate if it stumbles - or a plugged/bad MAP sensor. Clean the map
> > tube and hole in the throttle body as well.
> >
> > One caution: DO NOT turn the key on while the IAC is out and plugged
> > in - it throws the shaft clear accross the garage and it's hell to get
> > back together right!
> >
> > --
> > Will Honea <whonea@codenet.net>
>
>
09-12-2003, 12:51 AM
#13
Guest
Posts: n/a
Re: 4.0 idle stepper motor
I agree with Will... The stepper motor just controls idle speed. The only
way I can think of it causing stumble is if the idle was too low, but that
would be obvious.
Have you done all of the usual tune up items including plug wires?
Joe, 90XJ
"Homer Simpson" <me@privacy.net> wrote in message
news:bjrcj2$m7903$1@ID-185934.news.uni-berlin.de...
>
> "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
> > $30 for mine when I swapped it out a couple of years ago (got it from
> > Advanced Auto).
>
> Well I am in Canada and thinsg are expensive up here!
>
> Today was no better and I am still having the same problem after cleaning
up
> the stepper motor....
>
> I wonder what would happen if the stepper motor was engaged on a hot
engine
> and I pressed the accelerator, would it stumble?
>
> If so it would help diagnose the source. But if it did stumble when the
> stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> me if power is removed, it comes back in, and is not stuck.
>
> So confused! I at least have enough info to take it to my reputable
> mechanic.....
>
> My O2 sensor is fine so I guess I can look at the MAP aspects of it. Funny
> my Factory manual for my CJ was awesome for diags, but the XJ sucks
> beans.....
>
> If I don't figure it out it will go into the shop as it is now a daily
> occurance &^$#*#^$
>
> > Next, on the top of the throttle body there is a hole, about 1/4 inch
> > in diameter, on the fender side. That runs down to a plugged hole way
> > down on the side. Under that plug is a jet. use a knife point or ice
> > pick (remember those?) and pull the plug out. Turn the jet all the
> > way in counting the turns so that you can get it back to where it was.
> > Now, take the jet all the way out and clean that hole. It's an idle
> > air bypass and runs all the way down into the mainfold. Mine was
> > plugged solid and it took a lot of soaking and a long piano wire to
> > get it cleaned out. Put the jet back in and adjust it to where it
> > was. You can cover the access hole with silicone like the book says
> > or just forget it. Clean the contacts in the IAC plug with WD40 and a
> > stiff brush.
> >
> > The IAC opens and closes to allow more or less air to pass instead of
> > having to adjust the butterfly throttle plate t maintain an idle RPM.
> > If it fails in an appropriate position to maintain a decent cold idle
> > you see idle speed increase as the engine warms up or a high idle when
> > you come to a stop. If it fails closed then cold starts will be a
> > bitch and you will have to play with the throttle to keep it running
> > once you do get it started. It also accounts for the higher cold
> > start idle speed. I've rarely seen one cause stumbles on acceleration
> > other than on a dead cold engine. The O2 sensor is a more likely
> > candidate if it stumbles - or a plugged/bad MAP sensor. Clean the map
> > tube and hole in the throttle body as well.
> >
> > One caution: DO NOT turn the key on while the IAC is out and plugged
> > in - it throws the shaft clear accross the garage and it's hell to get
> > back together right!
> >
> > --
> > Will Honea <whonea@codenet.net>
>
>
way I can think of it causing stumble is if the idle was too low, but that
would be obvious.
Have you done all of the usual tune up items including plug wires?
Joe, 90XJ
"Homer Simpson" <me@privacy.net> wrote in message
news:bjrcj2$m7903$1@ID-185934.news.uni-berlin.de...
>
> "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
> > $30 for mine when I swapped it out a couple of years ago (got it from
> > Advanced Auto).
>
> Well I am in Canada and thinsg are expensive up here!
>
> Today was no better and I am still having the same problem after cleaning
up
> the stepper motor....
>
> I wonder what would happen if the stepper motor was engaged on a hot
engine
> and I pressed the accelerator, would it stumble?
>
> If so it would help diagnose the source. But if it did stumble when the
> stepper was engaged, when I unplug it, it immediately runs fine, which
tells
> me if power is removed, it comes back in, and is not stuck.
>
> So confused! I at least have enough info to take it to my reputable
> mechanic.....
>
> My O2 sensor is fine so I guess I can look at the MAP aspects of it. Funny
> my Factory manual for my CJ was awesome for diags, but the XJ sucks
> beans.....
>
> If I don't figure it out it will go into the shop as it is now a daily
> occurance &^$#*#^$
>
> > Next, on the top of the throttle body there is a hole, about 1/4 inch
> > in diameter, on the fender side. That runs down to a plugged hole way
> > down on the side. Under that plug is a jet. use a knife point or ice
> > pick (remember those?) and pull the plug out. Turn the jet all the
> > way in counting the turns so that you can get it back to where it was.
> > Now, take the jet all the way out and clean that hole. It's an idle
> > air bypass and runs all the way down into the mainfold. Mine was
> > plugged solid and it took a lot of soaking and a long piano wire to
> > get it cleaned out. Put the jet back in and adjust it to where it
> > was. You can cover the access hole with silicone like the book says
> > or just forget it. Clean the contacts in the IAC plug with WD40 and a
> > stiff brush.
> >
> > The IAC opens and closes to allow more or less air to pass instead of
> > having to adjust the butterfly throttle plate t maintain an idle RPM.
> > If it fails in an appropriate position to maintain a decent cold idle
> > you see idle speed increase as the engine warms up or a high idle when
> > you come to a stop. If it fails closed then cold starts will be a
> > bitch and you will have to play with the throttle to keep it running
> > once you do get it started. It also accounts for the higher cold
> > start idle speed. I've rarely seen one cause stumbles on acceleration
> > other than on a dead cold engine. The O2 sensor is a more likely
> > candidate if it stumbles - or a plugged/bad MAP sensor. Clean the map
> > tube and hole in the throttle body as well.
> >
> > One caution: DO NOT turn the key on while the IAC is out and plugged
> > in - it throws the shaft clear accross the garage and it's hell to get
> > back together right!
> >
> > --
> > Will Honea <whonea@codenet.net>
>
>
09-12-2003, 08:36 AM
#14
Guest
Posts: n/a
Re: 4.0 idle stepper motor
"Joe M" <txjoe59@yahoo.com> wrote in message
news:vm2k721ld7ip76@corp.supernews.com...
> I agree with Will... The stepper motor just controls idle speed. The only
> way I can think of it causing stumble is if the idle was too low, but that
> would be obvious.
> Have you done all of the usual tune up items including plug wires?
Oh ya...a couple of times already!
This AM I went and removed the airhorn. I covered the little air inlet
section for the ISM and accelerated with no problems, it just idled slower.
Which makes sense as the throttle is opening up and air is getting in. The
ISM in an output only on the ECU so there is no direct feedback regarding
its position.
Today I am thinking that my ISM operates correctly (or almost) as I have
absolutely no problems when idling. The issue comes up when the throttle is
open either while accelerating or when cruising. It always happens when the
engine is hot, or the ambient temp is hot. It could be sitting in the sun
all day and the engine is cold, and I have the problem after it starts.
The odd thing is is that it is immediately cured when I unplug the ISM. Like
instantaneous. Will brought up a good point I should have remembered.
Removing power to the ISM will not change its position as it is a stepper
motor.
Today's thoughts are that the ISM is shorting out sometimes causing problems
with the ECU, or my ECU is bad.
Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
I know it could be other things but I find it odd that disconnecting the ICM
fixes it.
#^%#
09-12-2003, 08:36 AM
#15
Guest
Posts: n/a
Re: 4.0 idle stepper motor
"Joe M" <txjoe59@yahoo.com> wrote in message
news:vm2k721ld7ip76@corp.supernews.com...
> I agree with Will... The stepper motor just controls idle speed. The only
> way I can think of it causing stumble is if the idle was too low, but that
> would be obvious.
> Have you done all of the usual tune up items including plug wires?
Oh ya...a couple of times already!
This AM I went and removed the airhorn. I covered the little air inlet
section for the ISM and accelerated with no problems, it just idled slower.
Which makes sense as the throttle is opening up and air is getting in. The
ISM in an output only on the ECU so there is no direct feedback regarding
its position.
Today I am thinking that my ISM operates correctly (or almost) as I have
absolutely no problems when idling. The issue comes up when the throttle is
open either while accelerating or when cruising. It always happens when the
engine is hot, or the ambient temp is hot. It could be sitting in the sun
all day and the engine is cold, and I have the problem after it starts.
The odd thing is is that it is immediately cured when I unplug the ISM. Like
instantaneous. Will brought up a good point I should have remembered.
Removing power to the ISM will not change its position as it is a stepper
motor.
Today's thoughts are that the ISM is shorting out sometimes causing problems
with the ECU, or my ECU is bad.
Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
I know it could be other things but I find it odd that disconnecting the ICM
fixes it.
#^%#
09-12-2003, 04:12 PM
#16
Guest
Posts: n/a
Re: 4.0 idle stepper motor
On Fri, 12 Sep 2003 12:36:41 UTC "Homer Simpson" <me@privacy.net>
wrote:
>
> "Joe M" <txjoe59@yahoo.com> wrote in message
> news:vm2k721ld7ip76@corp.supernews.com...
> > I agree with Will... The stepper motor just controls idle speed. The only
> > way I can think of it causing stumble is if the idle was too low, but that
> > would be obvious.
> > Have you done all of the usual tune up items including plug wires?
>
> Oh ya...a couple of times already!
>
> This AM I went and removed the airhorn. I covered the little air inlet
> section for the ISM and accelerated with no problems, it just idled slower.
> Which makes sense as the throttle is opening up and air is getting in. The
> ISM in an output only on the ECU so there is no direct feedback regarding
> its position.
>
> Today I am thinking that my ISM operates correctly (or almost) as I have
> absolutely no problems when idling. The issue comes up when the throttle is
> open either while accelerating or when cruising. It always happens when the
> engine is hot, or the ambient temp is hot. It could be sitting in the sun
> all day and the engine is cold, and I have the problem after it starts.
>
> The odd thing is is that it is immediately cured when I unplug the ISM. Like
> instantaneous. Will brought up a good point I should have remembered.
> Removing power to the ISM will not change its position as it is a stepper
> motor.
>
> Today's thoughts are that the ISM is shorting out sometimes causing problems
> with the ECU, or my ECU is bad.
>
> Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
>
> I know it could be other things but I find it odd that disconnecting the ICM
> fixes it.
>
> #^%#
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.
--
Will Honea <whonea@codenet.net>
wrote:
>
> "Joe M" <txjoe59@yahoo.com> wrote in message
> news:vm2k721ld7ip76@corp.supernews.com...
> > I agree with Will... The stepper motor just controls idle speed. The only
> > way I can think of it causing stumble is if the idle was too low, but that
> > would be obvious.
> > Have you done all of the usual tune up items including plug wires?
>
> Oh ya...a couple of times already!
>
> This AM I went and removed the airhorn. I covered the little air inlet
> section for the ISM and accelerated with no problems, it just idled slower.
> Which makes sense as the throttle is opening up and air is getting in. The
> ISM in an output only on the ECU so there is no direct feedback regarding
> its position.
>
> Today I am thinking that my ISM operates correctly (or almost) as I have
> absolutely no problems when idling. The issue comes up when the throttle is
> open either while accelerating or when cruising. It always happens when the
> engine is hot, or the ambient temp is hot. It could be sitting in the sun
> all day and the engine is cold, and I have the problem after it starts.
>
> The odd thing is is that it is immediately cured when I unplug the ISM. Like
> instantaneous. Will brought up a good point I should have remembered.
> Removing power to the ISM will not change its position as it is a stepper
> motor.
>
> Today's thoughts are that the ISM is shorting out sometimes causing problems
> with the ECU, or my ECU is bad.
>
> Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
>
> I know it could be other things but I find it odd that disconnecting the ICM
> fixes it.
>
> #^%#
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.
--
Will Honea <whonea@codenet.net>
09-12-2003, 04:12 PM
#17
Guest
Posts: n/a
Re: 4.0 idle stepper motor
On Fri, 12 Sep 2003 12:36:41 UTC "Homer Simpson" <me@privacy.net>
wrote:
>
> "Joe M" <txjoe59@yahoo.com> wrote in message
> news:vm2k721ld7ip76@corp.supernews.com...
> > I agree with Will... The stepper motor just controls idle speed. The only
> > way I can think of it causing stumble is if the idle was too low, but that
> > would be obvious.
> > Have you done all of the usual tune up items including plug wires?
>
> Oh ya...a couple of times already!
>
> This AM I went and removed the airhorn. I covered the little air inlet
> section for the ISM and accelerated with no problems, it just idled slower.
> Which makes sense as the throttle is opening up and air is getting in. The
> ISM in an output only on the ECU so there is no direct feedback regarding
> its position.
>
> Today I am thinking that my ISM operates correctly (or almost) as I have
> absolutely no problems when idling. The issue comes up when the throttle is
> open either while accelerating or when cruising. It always happens when the
> engine is hot, or the ambient temp is hot. It could be sitting in the sun
> all day and the engine is cold, and I have the problem after it starts.
>
> The odd thing is is that it is immediately cured when I unplug the ISM. Like
> instantaneous. Will brought up a good point I should have remembered.
> Removing power to the ISM will not change its position as it is a stepper
> motor.
>
> Today's thoughts are that the ISM is shorting out sometimes causing problems
> with the ECU, or my ECU is bad.
>
> Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
>
> I know it could be other things but I find it odd that disconnecting the ICM
> fixes it.
>
> #^%#
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.
--
Will Honea <whonea@codenet.net>
wrote:
>
> "Joe M" <txjoe59@yahoo.com> wrote in message
> news:vm2k721ld7ip76@corp.supernews.com...
> > I agree with Will... The stepper motor just controls idle speed. The only
> > way I can think of it causing stumble is if the idle was too low, but that
> > would be obvious.
> > Have you done all of the usual tune up items including plug wires?
>
> Oh ya...a couple of times already!
>
> This AM I went and removed the airhorn. I covered the little air inlet
> section for the ISM and accelerated with no problems, it just idled slower.
> Which makes sense as the throttle is opening up and air is getting in. The
> ISM in an output only on the ECU so there is no direct feedback regarding
> its position.
>
> Today I am thinking that my ISM operates correctly (or almost) as I have
> absolutely no problems when idling. The issue comes up when the throttle is
> open either while accelerating or when cruising. It always happens when the
> engine is hot, or the ambient temp is hot. It could be sitting in the sun
> all day and the engine is cold, and I have the problem after it starts.
>
> The odd thing is is that it is immediately cured when I unplug the ISM. Like
> instantaneous. Will brought up a good point I should have remembered.
> Removing power to the ISM will not change its position as it is a stepper
> motor.
>
> Today's thoughts are that the ISM is shorting out sometimes causing problems
> with the ECU, or my ECU is bad.
>
> Decisions decisions...... $75 for a wrecker ECU or $120 for a new ISM......
>
> I know it could be other things but I find it odd that disconnecting the ICM
> fixes it.
>
> #^%#
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.
--
Will Honea <whonea@codenet.net>
09-15-2003, 10:54 PM
#18
Guest
Posts: n/a
Re: 4.0 idle stepper motor
"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...
09-15-2003, 10:54 PM
#19
Guest
Posts: n/a
Re: 4.0 idle stepper motor
"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...
09-16-2003, 01:45 AM
#20
Guest
Posts: n/a
Re: 4.0 idle stepper motor
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>
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>