Would an idle air control valve cause a car to high?
A faulty Idle Air Control (IAC) valve can contribute to a car idling too high (or too low, or stalling). It's not the *only* possible cause of a high idle, but it's certainly a suspect. The IAC valve controls the amount of air entering the engine when it's idling, so a malfunction (sticking open, for example) could lead to excessive air intake and a resulting high idle.