When replacing the IAC you need to unhook the battery to allow the ecm to fully discharge so it can recalibrate things with the new IAC. Also in my case when installing a new Standard Ignition Parts IAC, they require setting the Pintle length to 1/18" from the mounting surface to the tip of the pintle before installing it. I cant say all aftermarket ones are like or not,however the OEM one is NOT adjustable.