SL2 idling high in park and neutral

Raina

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Mar 10, 2004, 10:14:45 AM3/10/04

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My 2002 SL1 has had this problem for over a year, the dealer and another mechanic have been unable to diagnose the problem since the car doesn't idle high in park and neutral when it's there. Last year it started to occassionally idle around 2200 RPM when put into park, hot or cold, about half the time. Now, most of the time, when it's been driven about 45 minutes, when placed in park or neutral, the RPM's jump up and stay there until I place it into gear. If I turn the car off, then back on, it idles normally, or may be high at first, then a few seconds later it comes down (still in park). While driving it, it also seems to be winding out the gears as I slow down, but I'm not sure if this is related. I hope someone out there can help me, thanks.

Dan Duncan

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Mar 10, 2004, 4:44:31 PM3/10/04

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Raina <raina...@yahoo.com> wrote:
> My 2002 SL1 has had this problem for over a year, the dealer and another mechanic have been unable to diagnose the problem since the car doesn't idle high in park and neutral when it's there. Last year it started to occassionally idle around 2200 RPM when put into park, hot or cold, about half the time. Now, most of the time, when it's been driven about 45 minutes, when placed in park or neutral, the RPM's jump up and stay there until I place it into gear. If I turn the car off, then back on, it idles normally, or may be high at first, then a few seconds later it comes down (still in park). While driving it, it also seems to be winding out the gears as I slow down, but I'm not sure if this is related. I hope someone out there can help me, thanks.

I have a 1998 SW2 with a manual transmission that does essentially
the same thing. The problem is intermittant and usually occurs
after driving for some time. The idle will kick up when I have the
clutch in or the car in neutral. If I shut it off and restart, the
problem immediately goes away. I've never been able to get a
good answer why, and the dealer of course can never duplicate
the problem. I have cleaned the throttle body and replaced the
coolant temp sensor. I'm pretty sure it's electronic in origin
just because "rebooting" the car makes it go away. Other than
that I can't really help you. I've just gotten used to it.

-DanD

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# Dan Duncan (kd4igw) da...@pcisys.net http://pcisys.net/~dand
# "Qui rides? Mutato nomine de te fabula narratur."
# (Why do you laugh? Change the name, and the story is told of you.) -Horace

Raina

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Mar 10, 2004, 6:59:49 PM3/10/04

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Thank you for replying. Sorry to hear there is no easy solution to our problem. If for some reason we solve it I'll keep you informed.

Thank you again,

Kirk Kohnen

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Mar 10, 2004, 9:03:05 PM3/10/04

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Did you replace the coolant temperature sensor because it failed?

If so, often the connector that goes to that sensor needs to be replaced
also. It corrodes, causing it to make poor contact. Poor contact translates
into high resistance. This gets read by the computer as a low temperature.
So, the engine idles up to "warm" it up.

On my 97 SL2, I had to replace the sensor. Things got better, but it still
exhibited the fast idle problem. Replacing the connector also fixed the
problem.

"Raina" <raina...@yahoo.com> wrote in message
news:c9deaffea779cc51...@localhost.talkaboutautos.com...

marx404

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Mar 11, 2004, 8:17:00 AM3/11/04

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I was just reading my Haynes and it said that problems revolving around the
functionality of the EGR valve (or related parts) may be causing this. What
do you pros think?

marx404

Raina

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Mar 11, 2004, 1:44:07 PM3/11/04

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Thank you Kirk for your suggestion. I haven't replaced the coolant temperature sensor, but I'll look into that.

richard hornsby

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Mar 16, 2004, 4:27:56 PM3/16/04

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I had what sounds like the same problem on my 1998 SL2 manual
transmission. It would run fine for a while, then all the sudden the
idle would jump to 2000-2200 and hang out there until I restarted the
car. Very weird, and seemingly intermittent. I would imagine you only
notice the problem in park/neutral because there is no drive train load
on the engine.

After several trips to the dealership (including all sorts of sensors
including coolant, etc replaced), I finally managed to get it into the
shop while it was idling high.

It turned out to be the _throttle body position sensor_ was feeding the
computer the wrong data - the throttle was physically in position X, but
the computer thought it was in position Y, so it ramped up the RPMs to
keep the engine at what it thought was idle.

HTH,
-rj

Raina

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Mar 18, 2004, 10:51:46 AM3/18/04

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Thank you Rich, sounds like I have the same problem you did, glad you solved yours. I really appreciate your help.
Thanks,
Raina

Dan Duncan

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Mar 18, 2004, 2:24:25 PM3/18/04

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richard hornsby <rhor...@osuedc.org> wrote:
> I had what sounds like the same problem on my 1998 SL2 manual
> transmission. It would run fine for a while, then all the sudden the
> idle would jump to 2000-2200 and hang out there until I restarted the
> car. Very weird, and seemingly intermittent. I would imagine you only
> notice the problem in park/neutral because there is no drive train load
> on the engine.

Wow, that's EXACTLY what I see and I have a 1998 SW2 manual.

> After several trips to the dealership (including all sorts of sensors
> including coolant, etc replaced), I finally managed to get it into the
> shop while it was idling high.

I was never able to get it in when it was idling high. I did
take it in twice complaining about the problem when it was still
under warranty. I'm out of warranty now, but would it still be
covered since the problem occurred under warranty? (My rear
window sprayer is the same story)

> It turned out to be the _throttle body position sensor_ was feeding the
> computer the wrong data - the throttle was physically in position X, but
> the computer thought it was in position Y, so it ramped up the RPMs to
> keep the engine at what it thought was idle.

Great, thanks! I'll keep that in mind. I'm due for some
100k maintenance.

-DanD

--
# Dan Duncan (kd4igw) da...@pcisys.net http://pcisys.net/~dand

# Sin lies only in hurting other people unnecessarily. All other 'sins' are
# invented nonsense. (Hurting yourself is not sinful- just stupid.)-Lazarus Long

Dan Duncan

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Apr 8, 2004, 6:29:19 PM4/8/04

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richard hornsby <rhor...@osuedc.org> wrote:
> It turned out to be the _throttle body position sensor_ was feeding the
> computer the wrong data - the throttle was physically in position X, but
> the computer thought it was in position Y, so it ramped up the RPMs to
> keep the engine at what it thought was idle.

Throttle position sensor giving bad data...

So it's having problems with its TPS reports? Hmmmm. Yeah.
Maybe it didn't get that memo.

-DanD

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# Dan Duncan (kd4igw) da...@pcisys.net http://pcisys.net/~dand

# "Mother Teresa stops short. Mother Teresa justifies what she does because
# of myth. Janet did what she did because it was right." -Jack Kevorkian,
# commenting on the death of his friend Janet Good.