4.0 idle stepper motor
 

Well you can read at the bottom my original problems and I think I have
narrowed it down somewhat!

On my 89 XJ it would idle fine, often when started up. Then I would give it
gas and it
runs really rough, like the timing is off or it is choked out real bad, the
engine does not rev.

I could not figure out the problem for the life of me. A minute later things
would be fine. It
would only happen 1 or 2 times a month, but now has become much more
frequent.

So I start undoing things when it happens and I find out that if I
disconnect the plug at the
idle stepper motor momentarily it works fine immediately. So I conclude
there is either something wrong with it, or my computer is shot. Some of the
articles on the subject indicate that when the stepper motor fails, you get
high reving.

With the stepper removed, I start it up and it revs really high. makes
sense, but I do not have that problem! So I clean it up real good and there
is some black crud on the parts
but the parts cleaner removes it all well, put it back together, and we will
find out in the next few days if it solved the problem.

I am guessing that at idle, the plunger is extended restricting the air
flow, but in my case does not get released for some reason when you
accelerate. Either bummed motor or just gummed up.

I wish I had the tool to engage the stepper motor, does anyone know what the
engine performance is like when it is stuck engaged? Does it studder
heavily?

Any insights appreciated and I will let you know what happens in the next
couple of days, and if it is not fixed I will pick one up from a wrecker to
try before I fork out $120 for a new one.

Bruce,
Jeep naked!





-----------------------original-------------->

From: Homer Simpson (root@127.0.0.1)
Subject: 89 XJ engine woes.....


View this article only
Newsgroups: rec.autos.makers.jeep+willys
Date: 2002-06-05 12:14:26 PST

Hey folks,

I posted this a year ago and have been unable to figure out what the
problem is....when my 89 XJ is warmed up, there are times that the
engine will only run smoothly while idling, any acceleration will result
in what sounds like the timing is all f&^*(d up! It just stutters. Then
I just let it idle anywhere from 1 - 5 minutes and then it runs fine.

I am about to take it to a dealer to get it fixed :( as it is
frustrating the heck out of me.

Bruce in Ottawa.

BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
like replacing an axleshaft deep in the woods/swamp.

mailto:bruce@phynetworks.comMessage 2 in thread
From: Mike Romain (romainm@sympatico.ca)
Subject: Re: 89 XJ engine woes.....


View this article only
Newsgroups: rec.autos.makers.jeep+willys
Date: 2002-06-05 13:12:51 PST


You have a throttle position sensor and if the connections on it, or if
it is dirty itself, it can cause that.

Maybe just go at all the electrical plugs and sockets coming off the
throttle body with a cleaner like WD 40 or something. My TPS was messed
up on my 88 and cleaning the connection worked great a couple years
back... Same for my CPS on the top drivers side of the bell housing.
It quit a couple weeks ago and I just cleaned the connection and so far
so good.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos:
Easter/02 http://www.imagestation.com/album/?id=4291929351
Jan/02 http://www.imagestation.com/album/?id=4292141347
Aug/01 http://www.imagestation.com/album/?id=4292076845
Day Trip Misc. http://www.imagestation.com/album/?id=4291902217

Homer Simpson wrote:
>
> Hey folks,
>
> I posted this a year ago and have been unable to figure out what the
> problem is....when my 89 XJ is warmed up, there are times that the
> engine will only run smoothly while idling, any acceleration will result
> in what sounds like the timing is all f&^*(d up! It just stutters. Then
> I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
>
> I am about to take it to a dealer to get it fixed :( as it is
> frustrating the heck out of me.
>
> Bruce in Ottawa.
>
> BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> like replacing an axleshaft deep in the woods/swamp.
>
> mailto:bruce@phynetworks.comMessage 3 in thread
From: CRWLR (CRWLRJEFF@YAHOO.COM)
Subject: Re: 89 XJ engine woes.....


View this article only
Newsgroups: rec.autos.makers.jeep+willys
Date: 2002-06-05 14:22:20 PST


What Mike said.

Re: 4.0 idle stepper motor
 

Ok....

What the heck are you driving and what engine????

An 89 XJ does not have a stepper motor, that is an 89 4.2L YJ puppy, it
has a throttle body with a TPS or throttle position sensor.

The TPS can be taken out and cleaned with carb cleaner. It is just your
basic rheostat.

It can be tested with a multimeter too. If you have that, I can post
the tests.

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

Homer Simpson wrote:
>
> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad, the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of the
> articles on the subject indicate that when the stepper motor fails, you get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker to
> try before I fork out $120 for a new one.
>
> Bruce,
> Jeep naked!
>
> -----------------------original-------------->
>
> From: Homer Simpson (root@127.0.0.1)
> Subject: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 12:14:26 PST
>
> Hey folks,
>
> I posted this a year ago and have been unable to figure out what the
> problem is....when my 89 XJ is warmed up, there are times that the
> engine will only run smoothly while idling, any acceleration will result
> in what sounds like the timing is all f&^*(d up! It just stutters. Then
> I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
>
> I am about to take it to a dealer to get it fixed :( as it is
> frustrating the heck out of me.
>
> Bruce in Ottawa.
>
> BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> like replacing an axleshaft deep in the woods/swamp.
>
> mailto:bruce@phynetworks.comMessage 2 in thread
> From: Mike Romain (romainm@sympatico.ca)
> Subject: Re: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 13:12:51 PST
>
> You have a throttle position sensor and if the connections on it, or if
> it is dirty itself, it can cause that.
>
> Maybe just go at all the electrical plugs and sockets coming off the
> throttle body with a cleaner like WD 40 or something. My TPS was messed
> up on my 88 and cleaning the connection worked great a couple years
> back... Same for my CPS on the top drivers side of the bell housing.
> It quit a couple weeks ago and I just cleaned the connection and so far
> so good.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos:
> Easter/02 http://www.imagestation.com/album/?id=4291929351
> Jan/02 http://www.imagestation.com/album/?id=4292141347
> Aug/01 http://www.imagestation.com/album/?id=4292076845
> Day Trip Misc. http://www.imagestation.com/album/?id=4291902217
>
> Homer Simpson wrote:
> >
> > Hey folks,
> >
> > I posted this a year ago and have been unable to figure out what the
> > problem is....when my 89 XJ is warmed up, there are times that the
> > engine will only run smoothly while idling, any acceleration will result
> > in what sounds like the timing is all f&^*(d up! It just stutters. Then
> > I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
> >
> > I am about to take it to a dealer to get it fixed :( as it is
> > frustrating the heck out of me.
> >
> > Bruce in Ottawa.
> >
> > BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> > like replacing an axleshaft deep in the woods/swamp.
> >
> > mailto:bruce@phynetworks.comMessage 3 in thread
> From: CRWLR (CRWLRJEFF@YAHOO.COM)
> Subject: Re: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 14:22:20 PST
>
> What Mike said.
>
> [Image]

Re: 4.0 idle stepper motor
 

Ok....

What the heck are you driving and what engine????

An 89 XJ does not have a stepper motor, that is an 89 4.2L YJ puppy, it
has a throttle body with a TPS or throttle position sensor.

The TPS can be taken out and cleaned with carb cleaner. It is just your
basic rheostat.

It can be tested with a multimeter too. If you have that, I can post
the tests.

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

Homer Simpson wrote:
>
> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad, the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of the
> articles on the subject indicate that when the stepper motor fails, you get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker to
> try before I fork out $120 for a new one.
>
> Bruce,
> Jeep naked!
>
> -----------------------original-------------->
>
> From: Homer Simpson (root@127.0.0.1)
> Subject: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 12:14:26 PST
>
> Hey folks,
>
> I posted this a year ago and have been unable to figure out what the
> problem is....when my 89 XJ is warmed up, there are times that the
> engine will only run smoothly while idling, any acceleration will result
> in what sounds like the timing is all f&^*(d up! It just stutters. Then
> I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
>
> I am about to take it to a dealer to get it fixed :( as it is
> frustrating the heck out of me.
>
> Bruce in Ottawa.
>
> BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> like replacing an axleshaft deep in the woods/swamp.
>
> mailto:bruce@phynetworks.comMessage 2 in thread
> From: Mike Romain (romainm@sympatico.ca)
> Subject: Re: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 13:12:51 PST
>
> You have a throttle position sensor and if the connections on it, or if
> it is dirty itself, it can cause that.
>
> Maybe just go at all the electrical plugs and sockets coming off the
> throttle body with a cleaner like WD 40 or something. My TPS was messed
> up on my 88 and cleaning the connection worked great a couple years
> back... Same for my CPS on the top drivers side of the bell housing.
> It quit a couple weeks ago and I just cleaned the connection and so far
> so good.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos:
> Easter/02 http://www.imagestation.com/album/?id=4291929351
> Jan/02 http://www.imagestation.com/album/?id=4292141347
> Aug/01 http://www.imagestation.com/album/?id=4292076845
> Day Trip Misc. http://www.imagestation.com/album/?id=4291902217
>
> Homer Simpson wrote:
> >
> > Hey folks,
> >
> > I posted this a year ago and have been unable to figure out what the
> > problem is....when my 89 XJ is warmed up, there are times that the
> > engine will only run smoothly while idling, any acceleration will result
> > in what sounds like the timing is all f&^*(d up! It just stutters. Then
> > I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
> >
> > I am about to take it to a dealer to get it fixed :( as it is
> > frustrating the heck out of me.
> >
> > Bruce in Ottawa.
> >
> > BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> > like replacing an axleshaft deep in the woods/swamp.
> >
> > mailto:bruce@phynetworks.comMessage 3 in thread
> From: CRWLR (CRWLRJEFF@YAHOO.COM)
> Subject: Re: 89 XJ engine woes.....
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 14:22:20 PST
>
> What Mike said.
>
> [Image]

Re: 4.0 idle stepper motor
 

Try spraying the entire intake around the throttle body with a good carb
cleaner like Berrymans, etc., until it shines like new. Particular attention
should be paid to the stepper motor port on the side of the t-body. It's
fairly common in modern engines for this port to crud up with carbon & gunk,
fouling the stepper and making it stick.

"Homer Simpson" <me@privacy.net> wrote in message
news:bjofkl$krjvs$1@ID-185934.news.uni-berlin.de...
> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give
it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad,
the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later
things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of
the
> articles on the subject indicate that when the stepper motor fails, you
get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and
there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we
will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what
the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker
to
> try before I fork out $120 for a new one.
>
> Bruce,
> Jeep naked!
>
>
>
>
>
> -----------------------original-------------->
>
> From: Homer Simpson (root@127.0.0.1)
> Subject: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 12:14:26 PST
>
> Hey folks,
>
> I posted this a year ago and have been unable to figure out what the
> problem is....when my 89 XJ is warmed up, there are times that the
> engine will only run smoothly while idling, any acceleration will result
> in what sounds like the timing is all f&^*(d up! It just stutters. Then
> I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
>
> I am about to take it to a dealer to get it fixed :( as it is
> frustrating the heck out of me.
>
> Bruce in Ottawa.
>
> BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> like replacing an axleshaft deep in the woods/swamp.
>
> mailto:bruce@phynetworks.comMessage 2 in thread
> From: Mike Romain (romainm@sympatico.ca)
> Subject: Re: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 13:12:51 PST
>
>
> You have a throttle position sensor and if the connections on it, or if
> it is dirty itself, it can cause that.
>
> Maybe just go at all the electrical plugs and sockets coming off the
> throttle body with a cleaner like WD 40 or something. My TPS was messed
> up on my 88 and cleaning the connection worked great a couple years
> back... Same for my CPS on the top drivers side of the bell housing.
> It quit a couple weeks ago and I just cleaned the connection and so far
> so good.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos:
> Easter/02 http://www.imagestation.com/album/?id=4291929351
> Jan/02 http://www.imagestation.com/album/?id=4292141347
> Aug/01 http://www.imagestation.com/album/?id=4292076845
> Day Trip Misc. http://www.imagestation.com/album/?id=4291902217
>
> Homer Simpson wrote:
> >
> > Hey folks,
> >
> > I posted this a year ago and have been unable to figure out what the
> > problem is....when my 89 XJ is warmed up, there are times that the
> > engine will only run smoothly while idling, any acceleration will result
> > in what sounds like the timing is all f&^*(d up! It just stutters. Then
> > I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
> >
> > I am about to take it to a dealer to get it fixed :( as it is
> > frustrating the heck out of me.
> >
> > Bruce in Ottawa.
> >
> > BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> > like replacing an axleshaft deep in the woods/swamp.
> >
> > mailto:bruce@phynetworks.comMessage 3 in thread
> From: CRWLR (CRWLRJEFF@YAHOO.COM)
> Subject: Re: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 14:22:20 PST
>
>
> What Mike said.
>
>
>
>

Re: 4.0 idle stepper motor
 

Try spraying the entire intake around the throttle body with a good carb
cleaner like Berrymans, etc., until it shines like new. Particular attention
should be paid to the stepper motor port on the side of the t-body. It's
fairly common in modern engines for this port to crud up with carbon & gunk,
fouling the stepper and making it stick.

"Homer Simpson" <me@privacy.net> wrote in message
news:bjofkl$krjvs$1@ID-185934.news.uni-berlin.de...
> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give
it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad,
the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later
things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of
the
> articles on the subject indicate that when the stepper motor fails, you
get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and
there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we
will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what
the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker
to
> try before I fork out $120 for a new one.
>
> Bruce,
> Jeep naked!
>
>
>
>
>
> -----------------------original-------------->
>
> From: Homer Simpson (root@127.0.0.1)
> Subject: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 12:14:26 PST
>
> Hey folks,
>
> I posted this a year ago and have been unable to figure out what the
> problem is....when my 89 XJ is warmed up, there are times that the
> engine will only run smoothly while idling, any acceleration will result
> in what sounds like the timing is all f&^*(d up! It just stutters. Then
> I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
>
> I am about to take it to a dealer to get it fixed :( as it is
> frustrating the heck out of me.
>
> Bruce in Ottawa.
>
> BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> like replacing an axleshaft deep in the woods/swamp.
>
> mailto:bruce@phynetworks.comMessage 2 in thread
> From: Mike Romain (romainm@sympatico.ca)
> Subject: Re: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 13:12:51 PST
>
>
> You have a throttle position sensor and if the connections on it, or if
> it is dirty itself, it can cause that.
>
> Maybe just go at all the electrical plugs and sockets coming off the
> throttle body with a cleaner like WD 40 or something. My TPS was messed
> up on my 88 and cleaning the connection worked great a couple years
> back... Same for my CPS on the top drivers side of the bell housing.
> It quit a couple weeks ago and I just cleaned the connection and so far
> so good.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos:
> Easter/02 http://www.imagestation.com/album/?id=4291929351
> Jan/02 http://www.imagestation.com/album/?id=4292141347
> Aug/01 http://www.imagestation.com/album/?id=4292076845
> Day Trip Misc. http://www.imagestation.com/album/?id=4291902217
>
> Homer Simpson wrote:
> >
> > Hey folks,
> >
> > I posted this a year ago and have been unable to figure out what the
> > problem is....when my 89 XJ is warmed up, there are times that the
> > engine will only run smoothly while idling, any acceleration will result
> > in what sounds like the timing is all f&^*(d up! It just stutters. Then
> > I just let it idle anywhere from 1 - 5 minutes and then it runs fine.
> >
> > I am about to take it to a dealer to get it fixed :( as it is
> > frustrating the heck out of me.
> >
> > Bruce in Ottawa.
> >
> > BTW, I finally sheared my first axleshaft in my 52 p/u! Nothing quite
> > like replacing an axleshaft deep in the woods/swamp.
> >
> > mailto:bruce@phynetworks.comMessage 3 in thread
> From: CRWLR (CRWLRJEFF@YAHOO.COM)
> Subject: Re: 89 XJ engine woes.....
>
>
> View this article only
> Newsgroups: rec.autos.makers.jeep+willys
> Date: 2002-06-05 14:22:20 PST
>
>
> What Mike said.
>
>
>
>

Re: 4.0 idle stepper motor
 

On Thu, 11 Sep 2003 00:27:03 UTC "Homer Simpson" <me@privacy.net>
wrote:

> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad, the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of the
> articles on the subject indicate that when the stepper motor fails, you get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker to
> try before I fork out $120 for a new one.

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). Two things come to mind from that long hassle.
First, remove the stepper from the throttle body and clean the shaft
on the stepper well then get the entire bore it goes into. Take the
inlet tube off and clean the opening from the top as well as from the
side. Gunk builds up on the seat and down into the bore.

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>

Re: 4.0 idle stepper motor
 

On Thu, 11 Sep 2003 00:27:03 UTC "Homer Simpson" <me@privacy.net>
wrote:

> Well you can read at the bottom my original problems and I think I have
> narrowed it down somewhat!
>
> On my 89 XJ it would idle fine, often when started up. Then I would give it
> gas and it
> runs really rough, like the timing is off or it is choked out real bad, the
> engine does not rev.
>
> I could not figure out the problem for the life of me. A minute later things
> would be fine. It
> would only happen 1 or 2 times a month, but now has become much more
> frequent.
>
> So I start undoing things when it happens and I find out that if I
> disconnect the plug at the
> idle stepper motor momentarily it works fine immediately. So I conclude
> there is either something wrong with it, or my computer is shot. Some of the
> articles on the subject indicate that when the stepper motor fails, you get
> high reving.
>
> With the stepper removed, I start it up and it revs really high. makes
> sense, but I do not have that problem! So I clean it up real good and there
> is some black crud on the parts
> but the parts cleaner removes it all well, put it back together, and we will
> find out in the next few days if it solved the problem.
>
> I am guessing that at idle, the plunger is extended restricting the air
> flow, but in my case does not get released for some reason when you
> accelerate. Either bummed motor or just gummed up.
>
> I wish I had the tool to engage the stepper motor, does anyone know what the
> engine performance is like when it is stuck engaged? Does it studder
> heavily?
>
> Any insights appreciated and I will let you know what happens in the next
> couple of days, and if it is not fixed I will pick one up from a wrecker to
> try before I fork out $120 for a new one.

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). Two things come to mind from that long hassle.
First, remove the stepper from the throttle body and clean the shaft
on the stepper well then get the entire bore it goes into. Take the
inlet tube off and clean the opening from the top as well as from the
side. Gunk builds up on the seat and down into the bore.

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>

Re: 4.0 idle stepper motor
 

"Mike Romain" <romainm@sympatico.ca> wrote in message
news:3F5FD285.AA436090@sympatico.ca...
> Ok....
>
> What the heck are you driving and what engine????
>
> An 89 XJ does not have a stepper motor, that is an 89 4.2L YJ puppy, it
> has a throttle body with a TPS or throttle position sensor.

Well according to my throttle body it does! it is an 89 XJ with a 4.0. The
facotry service manual covers it off, not that that would mean anything!

Thx for the tips and it has been acting up daily so I should have some news
to report tonight.

Re: 4.0 idle stepper motor
 

"Mike Romain" <romainm@sympatico.ca> wrote in message
news:3F5FD285.AA436090@sympatico.ca...
> Ok....
>
> What the heck are you driving and what engine????
>
> An 89 XJ does not have a stepper motor, that is an 89 4.2L YJ puppy, it
> has a throttle body with a TPS or throttle position sensor.

Well according to my throttle body it does! it is an 89 XJ with a 4.0. The
facotry service manual covers it off, not that that would mean anything!

Thx for the tips and it has been acting up daily so I should have some news
to report tonight.

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>