I have a 92 RS, auto, and recently the car has begun accelerating slightly on its own every now and then. I'll have the car in park, and the engine will reve slightly and I see the RPM gauge go up... if I'm moving at idle speed, i'll hear the engine rev, see the RPM gauge move a little bit, and the car will actually accelerate on its own. Its such a weird problem! I was wondering if the pedal was loose and somehow falling or something, causing the engine to rev up, but I'm sure thats not it because I pushed the pedal upward and it would still rev on its own. It does it about once every 10-30 seconds.The first time I noticed it was a few days ago when I turned on the air conditioner when it got warm, it was even worse and would rev every few seconds... after I turned the ac off, the problem stopped completely, but tonight it started doing it a bit even with the ac and vents off. My girl said that her 93 grand am does the same thing, but I had never heard of this problem before. What is it?

-Matt

 

If you turn the a/c on and you are at idle, you will get some surge depending on the head pressure of the a/c compressor and the cycling of the clutch. If it's doing it without the a/c on and no accessory load, then you may have a vacuum leak.

 

Also the A/C cycles when the defrost is turned on. Why? To take the humidity out of the air and your windshield.

Also your TBI gasket may be leaking. Its common on those cars.

 

Does this sound like a problem that would be expensive to repair?? Is it very serious and does it usually get worse or make the car impossible to drive?

-Matt

 

If it's the cycling of the a/c compressor, then it is normal and no repair attempt should be made. However, if it's starting to do it with no accessory load on the engine then you need to have it diagnosed to see if you don't have a trouble code in the system or a lazy IAC, 02 sensor, etc. Have it professionally diagnosed before your start throwing parts at it. Usually a dealer will give a diagnosis for about $35-45 dollars. That's a lot cheaper then guessing what it is and listening to inexperienced advice.

 

I agree with jzajac1...get it scanned for codes and see what comes up. We charge a 29.95 diagnostic fee to scan a car so it's not expensive and will probably save you a lot of time and trouble.