Sputter/Shake On Idle In Drive with AC On

Hey guys,

First time poster. Needing some help figuring out what’s going on with my 2005 Chevy Classic. Any time that the AC is on, and I’m in Drive but idling (stopped at a red light, parked in a parking space, etc), the engine sputters and shimmies. If I turn off the AC, it’s fine. Doesn’t do the same thing with the heat on, either.

I’ve got a short in my AC controls that causes the AC to go on and off from time to time and it fusses when it first comes on when it’s doing that, but the car is a pain even if it’s not shorting out. When I’m dring, I don’t have this trouble. It’s smooth as can be.

I thought at first it might be misfiring spark plugs so I checked those thoroughly, but that was before I noticed the AC connection. I’ve tried clearing out the air filter and stuff to see if maybe something was blocking my air intake and causing it, but that didn’t seem to help. I’m sort of stumped.

The AC seems to work fine on my car, it’s cold and blows hard, but it still seems like there’s an issue somewhere.

Any pointers or advice would be awesomely appreciated. Apologies if this is a dumb question, I’m just past green on doing my own car repair. I’m still not very good at diagnosing issues, but I can fix stuff with the best of them once I know what I’m fixing lol.


More than likely the problem is with the Idle Air Control valve.


The IAC valve controls the engine’s idle speed under all conditions.

For example, when you come to a stop with the AC on, the compressor puts a load on the engine. This load can cause the engine to idle rough. The job of the IAC valve is to slightly bump the idle speed up so the engine idles smoothly.


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Awesome! As soon as I can I’ll swap that out and let you know if it worked. Thanks for the input! That sounds exactly like my problem :slight_smile: