The idle air control valve, sometimes known as an IAC, is an electrical actuating device designed to electromechanically control engine idle speed. It is an essential part of the vehicle engine management system, integrated into a bypass housing or located on or near the throttle body assembly. The idle air control valve allows a measured amount of air to bypass the throttle plate/butterfly when it is closed, enabling the ECU to accurately control the idle speed of the vehicle’s engine.