Stalling on 1990 Buick LeSabre

Why does the engine stall occassionally when the air cond is on? No codes. Have replaced crank sensor, throttle position sensor and ecm since these parts may not give out codes when stalling. It stalls when in drive but will start back up immediately. Problem happens only when the air cond is on but cannot duplicate when the car is in the repair shop. No starting problems. Fuel pressure is fine.

by in Roselle, IL on March 16, 2010
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1 answer
ANSWER by , March 16, 2010
I hate replacing parts without testing them and confirming they are bad. Your engine has an idle speed control valve mounted on the throttle housing. When electrical loads are applied or the air conditioning is turned on the computer in your car receives a signal a "load" has been turned on and should compensate by raising the idle speed, perhaps there is a problem with this control valve or associated wiring. .