90 idle gone wrong
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Joined: Mar 2005
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90 idle gone wrong
My car, for the third time has mysteriously lost its idle. It comes and leaves without warning. Cracking open the throttle with a spacer allows it to idle. Cleaning the throttle body/ IAC passages did nothing at all. I know it shouldn't be connected, but code 74 for the dimmer circuit sets when it goes astray.
Help!
Car has 37K miles
6 spd
Help!
Car has 37K miles
6 spd
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Unless the IAC needs to be replaced I would suspect a vacuum leak, like maybe through a leaking EGR diaphram.
BTW, when you cleaned and replaced the old IAC module, did you also reset base idle to 450RPM??
BTW, when you cleaned and replaced the old IAC module, did you also reset base idle to 450RPM??
Thread Starter
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Joined: Mar 2005
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Thanks for the reply!
I did the 5 seconds on with pedal slightly depressed/ 10 seconds off routine.
Would a vacuum leak manifest as a problem that is absent for months, then constant for days/weeks, then absent for months again?
I did the 5 seconds on with pedal slightly depressed/ 10 seconds off routine.
Would a vacuum leak manifest as a problem that is absent for months, then constant for days/weeks, then absent for months again?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
That method will set the TPS but you still need to set base idle to 450rpm with the IAC pintel fully extended.
Vacuum leaks can be intermittent, depending on source. You may be able to catch it with a vacuum gauge on a manifold port. Of course manifold vacuum will fluctuate with entine idle speed too.
Vacuum leaks can be intermittent, depending on source. You may be able to catch it with a vacuum gauge on a manifold port. Of course manifold vacuum will fluctuate with entine idle speed too.
