2003 Trailblazer - Ac On Stalls Engine

[Wilmero]

Hello, and thank you for your time. I have a 2003 Trailblazer 4200 with the straight 6. The engine, (with 70k miles) idles at about 700rpm but when I turn the heater on the engine stalls, when the AC is cycling the engine rpm's fluctuate (hunts) and stalls. I have replaced the Fuel filter and air cleaner. I have a suspicion that the problem may be the AC pump. Where should I start looking?

 

Thanks again.

 

Rich

[C6Racer]

Does the engine stall only if it's idling or do you feel a considerable load when you're driving and the compressor kicks in? It it also puts a strain on the engine while you're driving then I'm afraid the compressor may have suffered a catastrophic failure. If it only affects the engine at idle then I would check the condition of the IAC (Idle Air Control) valve. It should be located on the throttle body next to the TPS. I'm not familiar with these engines, so I'm not sure. The IAC valve is supposed to open up to increase the idle when the A/C compressor is engaged. It may be stuck or the idle air passage may be very dirty or clogged up. I would removed the throttle body and give it a thorough cleaning with TB cleaner as this part should be maintained clean enough to eat off of. I clean mine every 15k miles or so because it gets dirty very quickly. Make sure you have a new TB gasket handy if you do this because I'm not sure if it's re-useable like mine.

Hope this helps. Good luck!