2003 Trailblazer - Engine stalls at idel w/AC turned on

2003 CHEVROLET TRAILBLAZER
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MEESTERBLACK
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2003 Chevy Trailblazer with approx. 120,000 miles. Paid off literally three weeks ago, exactly five years old. No major repairs to date with the exception of yesterday (replaced dead alternator), so can't complain too bad. Following alternator replacement (should be unrelated to this, but who knows), engine stalls when idling if A/C is turned on. A/C runs fine when idled at > 1000 RPM or while driving, but as soon as you stop... it stalls. One word of note: while replacing alternator, I had to push a bit on one of the A/C hoses that connects the A/C compressor to the radiator. I wonder if I could have bent the metal part of the hose just enough to restrict refrigerant flow, but very doubtful!! Other than that, this does not make sense. I disconnected battery during alternator change, and I don't suspect any computer brain issues, but again -- who knows! HELP !! Thanks :)

-Mike-
Sep 20, 2007 at 10:31 AM
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KJHUDSON
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Im having the same problem. I was told that the PCM needs to be reprogramed after battery has been disconnected. There is a process in the Haynes manual to reset it but it hasnt worked for me. Chevy dealership doesnt have a clue and wants $100 to reprogram.
Sep 26, 2007 at 4:34 AM
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MEESTERBLACK
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Well, I had to take my Trailblazer to the dealer to get it fixed. I was hoping I wouldn't have to, but alas the problems I had were beyond my (rather capable) technical abilities.

They told me the same thing -- the PCM needed to be reprogrammed after battery disconnection as it forgets how to idle properly. As I understand it, the PCM "learns" over time how to idle correctly for your vehicle and its environmental conditions. Once that memory is lost...

Also, after 120,000 miles, my throttle body/intake was so gummed up that the throttle body itself couldn't make the necessary fine adjustments to the idle speed to keep the engine running under A/C compressor load.

All in all, $100 for the PCM reprogramming and $200 for a full-blown fuel injector/throttle body cleanup (I called it priced it at an auto parts store to do the latter myself -- $200 for the kit).

Oh well!! Better than a whole new A/C compressor (which is what I thought was wrong!)
Sep 26, 2007 at 4:43 AM
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