idle problem when A/C is on?

I have a 94 3000GT Base and when at a stop with the AC running, it idles way low, but no check engine lite? Anyone had this problem??

sounds like you may just need a tune up

It just had a tune up at the mitsubishi dealership, new belts, plugs and etc., 3 months ago, I had someone to mention a sensor but I have no idea which one it would be. I just noticed a few weeks ago due to having to run the AC. Suggestions? other than the obvious to take it to a mechanic, I kinda need an idea of how much $ this could get into. Thanks

Well, when my AC is on, my RPM kinda "jumps" a bit. I mean, as soon as I turn it on, I see it "rise" really quick and usually goes back to normal, but I could tell that some of the power is gone. But when I turn it off, everything's normal again. This is though, I don't use my AC all that often...

yea, my rpm with a/c on it right at 1000.

Your IAC (Idle air control) is not funtioning properly. If you turn the AC on then your idle should increase. To test it cycle your steering wheel back and forth. Your idle should increase with this motion. If not then it is a basic verification of the IAC not working. There is a proper test method on stealth316.com.

Thanks, I'll check into it. Is the IAC a sensor of some sort or a part that you can replace? Thanks

IAC is a little stepper motor that is located on the side of the throttle body. It can be cleaned, as sometimes thats all thats needed, or replaced. They are not cheap though. I bought a used one when mine finally died for good.