Idle Speed/Throttle Actuator - Electronic: Description and Operation

PURPOSE/OPERATION
The idle air control motor maintains idle speed by compensating for loads placed on the engine. The IAC motor is a stepper motor that regulates the amount of air taken in through the bypass circuit of the intake manifold by opening and closing the motor valve located in the air passage. The engine control module supplies voltage in one polarity direction, which turns the motor in a particular rotation. The motor shaft is connected to a screw that when turned, opens the passage by moving the pintle. When the ECM reverses polarity, the passage is closed in the same manner. The ECM uses several sensor inputs to determine the operating condition of the engine and the loads being placed on it. The ECM adjusts the idle for air conditioning and automatic transmission loads, and controls fast idle for cold start. The ECM uses the IAC motor to make all of the adjustments to idle speed.