I have a problem with my 92 camaro (it is the 305 RS) maybe its a common one im not sure. Anyways here is the problem when I am sitting still idling and I turn the AC my engine starts dragging it feels then reving way up. I don't mean a little 50 rpm rev increase either its more like a couple thousand. Then the engine drags back down and does the same thing. The whole process takes maybe 4 seconds the repeats. The AC does actually still work though.

 

AC puts a load on the engine, so there is a mechanism in place to slightly increase rpm's to compensate. But it should not be raising rpm's like that, and should not be allowing such a fluctuation.

But I can't help anymore than saying that - I'm no expert on the A/C system and those pressure switches that control that stuff and such - someone else will chime in Im sure.

 

Mine does the same exact thing, except it is only like 500rpm's..a real pain because I can feel it down the road dropping/gaining rpm and makes me sway back and forth. I would rather 95* heat than swaying.

 

In a 92 I believe the computer controls the RPMs when A/C is commanded on. But I wouldn't know where to even begin looking.

 

Yeah, but I beleive the ECM gets input from the pressure switches on the A/C somehow.

 

It does, I'm not sure what ECM you have, but it's usually a green wire. When the AC clutch kicks in, it's supposed to send 12v to that wire, which in turn signals the ECM to raise the idle speed by about 100 rpm.

It sounds like this wire may not be seeing a signal when the AC is turned on, and the AC compressor is choking the engine down to almost dying, then the ECM tries to prevent it from dying by giving it a shot of fuel, which revs the engine back up. Rinse, repeat.

What ECM do you have? We can track down which pin on your ECM should be getting a signal, and you can test to see whether that's actually working or not...

It's also possible that you have a severe restriction in the AC system itself, and it's actually causing the engine to labor too much at idle, to keep compressing. Usually the high-pressure cutoff switch will prevent this though...

Do you have a set of AC manifold gauges? If not, you can "Rent" them for free from autozone. We should make sure that your pressures are normal as well...

 

Im not sure what ECM could you tell me how to determine my ECM. Also what does ECM stand for? Electronic Control Module. Im not sure it is the first option you said (how ever I could very easily be wrong) because it even does it when im driving down the road as TheMonster described jerking back slightly then going forward, however I also hear a little hiss for about 1/2 a second durring that cycle its very quite and could just but the sound of the compressor runnning.

 

ECM is the Engine Control Module. If it's happening while you're driving down the road, it's not going to be the ECM though, it's definitely mechanical.

You need to get ahold of a set of AC Manifold Gauges, and see what's going on inside the system. Like I said, Autozone will rent them for free. You just pay a deposit on them, and you get your money back when you bring them back to the store.