Car stalling with A/C on?

The IAC certainly would cause the engine to stall when a strong load is put on at idle such as the air conditioning. Simply put, it varies the air to the engine to control the engine RPM at idle. If it doesn't work, the engine will either race or stall as loading changes at idle. Since you bought a new one, you might as well put it on. I would have tested it to make sure that it was the problem first.

Alright, I can understand where the line of thinking comes from that would lead to the IAC, but I have another view to give. You say your vehicle runs fine when the AC is not on, and it holds its idle fine. See, the IAC is not just open at 1 spot all the time, it will change as needed, and the fact that your vehicle changes this setting and makes it run fine all the time would lead me to think the IAC is not bad.

Your problem arises when the AC is turned on. On most vehicles, when the computer is given the signal from the switch that the AC is being turned on, it will anticipate the added load of the compressor on the engine and set the idle up to compensate. It would seem to me that your computer is not setting the idle up as it should, this is whats causing your idle problem with the AC on.

So, I'm gonna have to say my first thought is that the IAC is not the problem, but I have been wrong many times before. I hope this helps some.

And a side note. I try not to jump on people for saying things that might seems stupid, so I won't jump on the guy who asked what a Air Idle Control Valve is. In the auto industry, it is typically called an IAC. And in his defense, if he is just a do-it-yourselfer and works primarily on Ford products, he may not have heard the term because Ford likes to call it BPA or By Pass Air. What I'm saying is that maybe he just knows it by a different name, I'm sure he knows what it is, maybe he just had a brain-fart, Lord knows its happened to me more times then I care to remember.

What exactly is an Air Idle Control valve? What sounds wrong is an Idle-up control that adds a few revs to your car when the AC is on. It isn't a valve, it's a servo that gives a bit more tug on the throttle.

If you bought this Air Idle thing and haven't put it on, go ahead and install it and see if that sets things aright. Having spent the money, it's doing you no good sitting on the counter. Besides, it may be about time to replace that regardless of what it is.

JILLINA this is a VERY simple problem with a CHEAP and easy solution!! Take $@0 to the nearest QUICKY LUBE, and have them celan out your THROTTLE BDOY and esp the IDLE AIR CONTROL VALVE> The IAC fine tunes the AIR portion of your injection system, and NO gas additives will celan it up. It is RESPONSIBLE for adding AIR to the injected fuel and ALSO to raiseu yoru IDEL speed when the A/C is truned on. Once done, remove the factory JUNK DELCO pllugs and instal aset of BOSCH IRIDIUM spark plugs. This will ENHANCE Low engine power, and yoru car wil have MORE pep with the A/c turned ON than it did with the A/c truned OFF! Gm plugs are NOT very effiecnt and just enough to get ht job done, thank you. PLug making is an ART that EUROPE and JAPAN have mastered. It is VERy simple, but true, the TYPE of plug used will SAVE GAS save your CONVERTER and O2 sensors and add more LIFE to your engine as LESS carbon is made within it. GOO DLUCK!!!

The ECM should be getting a signal to up the idle when the AC is on.

There is either a disconnected wire some place, faulty relay or switch.

I don't have a wiring diagram to sort it out, maybe someone else does.

check 4 a broken vacuum line,or make sure your air control valve is adjusted properly,you can get a can of carb cleaner it will make your car temporearily run smoother if a vac leak is present