Idle Speed/Throttle Actuator - Electronic: Description and Operation

By-Pass Air Control Valve:

PURPOSE
The bypass air control valve modifies idle speed to bring it as close as possible to preset limits.

LOCATION
The control valve is located under the intake manifold, towards the rear of the engine.

OPERATION
Whenever the engine is running the control valve receives a duty cycle type signal from the ECU. Engine speed is modified by the duty control valve. By altering the amount of air allowed to bypass the throttle plate, idle speed is adjusted as needed.

A second air passage is controlled by a bimetallic spring. The spring senses heat from a coolant passage in the valve. During cold engine temperatures the spring opens the air cut valve and raises idle speed.