Idle Speed Control

Idle speed is kept at the optimum speed by controlling the amount of air that by-passes the throttle valve in accordance with changes in idling conditions and engine load during idling. The ECM drives the Idle Speed Control (ISC) motor to keep the engine running at the pre-set idle target speed in accordance with the engine coolant temperature and air conditioning load. When the air conditioning switch is turned off and on while the engine is idling, the ISC motor operates to adjust the throttle valve by-pass air amount in accordance with the engine load conditions in order to avoid fluctuations in the engine speed.