Idle Speed/Throttle Actuator - Electronic: Description and Operation

During cold engine operation, it is necessary to increase the engine idle speed in order to shorten the engine warm-up period. Fast idle is achieved by a temperature controlled air valve mounted on the left side of the intake manifold. This valve opens and closes a gate valve by means of a bimetal strip and a heater coil. At low temperatures, the gate valve is normally open. When the engine starts, air from the air cleaner bypasses the throttle valve and flows through the air valve into the intake plenum. In this condition, intake air quantity is increased causing the engine to idle faster than normal. As the engine reaches operating temperature, the bimetal strip is heated by engine coolant and an electric heater coil.