abnormally high idle speed
10-01-2014, 11:28 AM
#1
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Car: 86 IROC
Engine: 5.0 TPI
Transmission: 700-R-4
Axle/Gears: 2.73 open
abnormally high idle speed
recently my 86 TPI car has developed a high idle speed. around 1500 or so. now I have a clean throttle body, a new IAC and the TPS is spot on. also there are no vac leaks. I performed the min idle adjustment per the FSM and the condition persists. anyone have any ideas??
10-01-2014, 11:55 AM
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Car: 88GTA
Engine: 5.7TPI
Transmission: Auto
Axle/Gears: 3.27
Re: abnormally high idle speed
Just a "way out there" thought Rusty.... throttle shaft bushings nice..not sucking in air from there? Blades closing all the way? Just some idear"s
10-05-2014, 04:45 AM
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Car: 1988 GTA
Engine: LB9
Transmission: T5
Axle/Gears: 3.45
Re: abnormally high idle speed
Is the new IAC working as commanded? When you apply load by putting it in drive or turning the A/C on, does the IAC compensate?
10-05-2014, 08:00 AM
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Car: 86 IROC
Engine: 5.0 TPI
Transmission: 700-R-4
Axle/Gears: 2.73 open
Re: abnormally high idle speed
in a word no,the idle speed stays pretty much at 1200 or so. no matter what.i can do the min idle air and have it perfect UNTILL I button it all back up.then its idle is way too high. what would cause this. I used a quality IAC. and all else is ok too .
10-05-2014, 10:31 AM
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Car: 1988 GTA
Engine: LB9
Transmission: T5
Axle/Gears: 3.45
Re: abnormally high idle speed
Well, if it is at 1200 RPM in neutral, and then also stays at 1200 RPM in drive, the IAC motor is obviously moving out in order to keep it there in order to maintain speed. That's good news.
I would suspect a vacuum leak, but you sound quite confident that all is sealed up.
Is it possible that the ECM thinks the engine is always cold, so it's keeping the idle speed up? Do you have a scan tool to check coolant temp?
I would suspect a vacuum leak, but you sound quite confident that all is sealed up.
Is it possible that the ECM thinks the engine is always cold, so it's keeping the idle speed up? Do you have a scan tool to check coolant temp?
10-05-2014, 10:52 AM
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Car: 86 IROC
Engine: 5.0 TPI
Transmission: 700-R-4
Axle/Gears: 2.73 open
Re: abnormally high idle speed
Well, if it is at 1200 RPM in neutral, and then also stays at 1200 RPM in drive, the IAC motor is obviously moving out in order to keep it there in order to maintain speed. That's good news.
I would suspect a vacuum leak, but you sound quite confident that all is sealed up.
Is it possible that the ECM thinks the engine is always cold, so it's keeping the idle speed up? Do you have a scan tool to check coolant temp?
I would suspect a vacuum leak, but you sound quite confident that all is sealed up.
Is it possible that the ECM thinks the engine is always cold, so it's keeping the idle speed up? Do you have a scan tool to check coolant temp?
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