I had the same prob. I put a new one on and it did the same thing. The Iac has 2 parts to it. The valve and the thermostat on the bottom of the throttle body. I had to disassemble it [the thermostat] and clean it. there is a threaded plastic piece inside that needs to be right. youll see what I mean. It sucks because you very seldom have to buy one. just clean it and they usually work.