Idle Speed/Throttle Actuator - Electronic: Description and Operation

Idle Air Control Valve Assembly (IAC):

Engine idle speed is controlled by the ECM through the Idle Air Control (IAC) valve mounted on the throttle body. The ECM sends voltage pulses to the IAC motor windings causing the IAC valve pintle to move "IN" or "OUT" a given distance (a step or count) for each pulse. The pintle movement controls the air flow around the throttle valves, which in turn, controls engine idle speed.