My 03 malibu has 70000 mls on it and a few weeks ago it started to idle high (around 2800-3400 rpm) after warm up. Sometimes it will stop diong it completely and other times it will fluctuate. I replaced IAC valve with an aftermarket one and it ran fine for about 5 days and started to do it again. Anyone else that has had this problem and knows a fix some help would be appriciated.:confused::banghead:

Wiggle the throttle position sensor and check if it came loose. Usually when they go the idle speed will go up and down. You can use a DVOM and watch the ohms as you move the throttle.

My 99 Malibu, 3.1L with 110,000 km did the same thing. As well, the engine light stays on (Code 0442). Two weeks ago I replaced the AIC and cleaned the throttle plate but no improvement. After this, I pulled the codes P0122 and 0113. I then replaced the TPS (throttle position sensor) and IAT (intake air temp sensor). The high idle has not come back. I will wait one more week to satisfy myself that the problem is resolved. PS: I always have the heater control set to defrost/floor. I know this causes the A/C compressor to engage and at first thought this might contribute to the problem, but now I don't think so. PPS: The engine light is still on, even after repeatedly clearing the code and installing new GM gas cap. That's my next challenge. Car runs great, even with the standard equipment tick-tick-tick of piston slap. :smile: