Mechanics

HIGH IDLE AND REVVING?

2003 Pontiac Grand Am • 80 miles

I have a 2003 Pontiac Grand Am 3.4 liter. Sometimes the engine starts revving high uncontrollably. It doesn't happen all the time, but when it does happen, it does it sometimes when I start the car, or when i'm driving down the road, or when i'm sitting at a stop light. I tried replacing the idle air control valve and the throttle positioning sensor, but it still does it. Any ideas?
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Jsc21583
September 4, 2011.



Did you clean the throttle-body? Any applicable trouble codes? How high do the rpms go? Maybe a vacuum leak? If it happens at idle in park, block off the mouth of the throttle body, see if any effect on the idle, should be a big effect. If no effect, you have false air getting in there from somewhere.

JDL
Sep 4, 2011.
It's actually my fiance's car. Her dad said he cleaned the throttle body. I scanned the car with a OBD-II scanner and it said no trouble codes. Someone told me it could be a computer problem and I may need to have the computer reflashed (whatever that means?) I've listened to it while it was running at idle and I don't hear any vaccume leak but I could be wrong.

Tiny
Jsc21583
Sep 4, 2011.
Yeah, if the problem is intermittent, it can be a pain to track down. Can you put a scanner on it that shows live engine data?

JDL
Sep 4, 2011.
Are you losing engine coolant or engine oil? Might be an issue with lower intake gasket?

JDL
Sep 4, 2011.
I think there might be a leak in the lower intake gasket because I found a little oily residue in the reservoir a while back. I have since flushed the coolant, but obviously that wouldn't solve the problem of the gasket leak. How would the lower intake gasket leaking affect the idling?

Tiny
Jsc21583
Sep 4, 2011.
It may cause a vacuum leak. Vacuum leaks can effect your idle. I can't see much from here, I can only make suggestions.

JDL
Sep 4, 2011.
Yeah that actually makes sense. Vacuum leak=erratic idle. Thanks for the suggestions, appreciate it!

Tiny
Jsc21583
Sep 4, 2011.
Hope you find the issue?

JDL
Sep 4, 2011.
Repaired the lower intake gasket, didn't work.

Tiny
Jsc21583
Sep 7, 2011.
Put a scanner on it, that shows live engine data. Look at idle and idle required, they should be close to the same. You can also look to see if anything is being commanded ON, like the ac. Also, I'd have to look at sensor signals, to see if anything doesn't look right?

JDL
Sep 7, 2011.
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