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?
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.
September, 4, 2011 AT 7:46 PM
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.
September, 4, 2011 AT 8:05 PM
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?
September, 4, 2011 AT 8:10 PM
Are you losing engine coolant or engine oil? Might be an issue with lower intake gasket?
September, 4, 2011 AT 8:20 PM
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?
September, 4, 2011 AT 8:26 PM
It may cause a vacuum leak. Vacuum leaks can effect your idle. I can't see much from here, I can only make suggestions.
September, 4, 2011 AT 8:45 PM
Yeah that actually makes sense. Vacuum leak=erratic idle. Thanks for the suggestions, appreciate it!
September, 4, 2011 AT 8:58 PM
Hope you find the issue?
September, 7, 2011 AT 1:29 PM
Repaired the lower intake gasket, didn't work.
September, 7, 2011 AT 2:14 PM
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?