When the air conditioner compressor kicks in, the idle drops below 400 RPM. It appears that the computer figures out the engine is about to stall then throttles up instead of kicking the idle up as soon as the compressor clutch engages. This lag results in an up/down idle and usually results in a stall. There is no lag when I step on the pedal. I noticed this problem after I replaced the battery. 60k miles, engine runs perfectly otherwise and the air works fine.
Ideas?