Cavalier Having A/C and Engine Problems

I have a 2002 Chevrolet Cavalier that recently is having a/c and engine problems.
One problem is that when the a/c is on the car will idle very badly- possibly varying 300-400 RPM. It will do this until the air is turned off or it is given more gas.
The second problem is when trying to keep the car at a constant speed with the a/c on the car will vary 200-300 RPM until the a/c is turned off or it is given more gas.
The last problem is when the a/c is on and no more gas is given to the car the a/c will start to blow out hot air. However, when gas is given to the car (probably has to be at about 1500 RPM) the a/c will blow out cold air.
The car is a 2.2L 4 cylinder. The car has had the check engine light on in the pass but I had cleared it (it was the o2 sensor) several times. But recently it has not been coming back on. I don’t know if this has anything to do with it, considering it only happens with the a/c on, but I thought that I would mention it. The car runs fine without the a/c on (idles well and drives good at constant speeds).
Does anyone have any suggestions with whats wrong with it?

Sounds like your compressor is intermittently binding up loading the engine via the serpentine belt.

Does that mean that the compressor is ruined?

The problem might be with the Idle Air Control valve.

The IAC valve is what keeps the idle speed constant under all conditions.

For example when the AC is turned on, the IAC valve is suppose to move to a position where the load of the compressor on the engine doesn’t allow the engine to run rough at idle. If the RPM"s change at idle with the AC on it means the IAC valve is hunting for the proper position. If the IAC valve is hunting for the proper position at idle, it can also hunt for the proper position while driving.

This means as the IAC valve hunts for the proper position while driving, it’s letting extra air past the open throttle plate. The O2 sensor see’s this extra air entering the engine so the computer adds more fuel to compensate for this extra air. and the RPM’s change.

If the IAC valve can’t keep the engine at a constant RPM when idling, the compressor can’t keep the pressures constant and the AC stops working until you step on the gas.

I bet if you replace the IAC valve it’ll fix your problems.


Maybe - Has anybody charged it recently. possibly overcharging it? Is it making any growling noises when the AC is on?

It was charged several years ago, but it just very recently started having the problems. I do not notice any growling noises when the a/c is on. From what I can tell it is sounds normal.

About the only thing I can suggest is to have the AC pressures checked with gauges by a mechanic. The fact that your idle is normal when the AC is off leads me to doubt the IAC is malfunctioning, but it could be.

It could also have a vacuum leak. The best and easiest way to determine this is by connecting a vacuum gauge.
If a leak exists the best way of finding it would be with a smoke detector and lacking that, pinching off hoses until it’s narrowed down.

Make sure the radiator fan appears to be operating correctly with the A/C on in case this is an issue with the high side pressure spiking because of an inoperative or slow running fan.