There is no adjustment with electronic fuel injection. Idle speed is controlled by the Engine Computer. If the engine runs rough at any time, you have a misfire unless the idle speed is really low. Address that misfire and the idle speed will be okay.
If the idle air control valve has an electrical problem, that will be detected by the Engine Computer which will set a diagnostic fault code. That may not turn on the Check Engine light because it won't affect emissions. You should get a nice "idle flare-up" to 1500 rpm when you start the engine. If you do, the valve is working. If you don't, it could be blocked with carbon. Your mechanic can connect a scanner to run the idle speed up and down to verify the IAC is working and the computer has control of it. If it doesn't respond when the computer tries to raise the idle speed, suspect the valve is sticking.
Oct 12, 2013 at 7:00 PM
