Idle Up Control Valve: Description and Operation

Idle Boost Valve:

The Idle Speed Boost Valve is located at the rear of the engine compartment just forward of the ignition coil. The Idle Speed Boost Valve maintains the idle speed within a 300 rpm range, compensating for various engine loads (cooling fan, etc.) while at idle. A second valve is fitted on cars with air conditioning to boost the idle speed when the A/C is turned on. The electrically operated valves allow additional air to bypass the throttle plate and increase the idle speed whenever it drops below 750 rpm. Above 1050 rpm, the valves close and the idle speed is reduced.

The Idle Speed Boost Valve is a solenoid valve controlled by an electronic control unit located on the fuse/relay panel that turns the valve on and off according to an engine speed signal from the ignition coil. Below 750 rpm, a control unit signal opens the valve. The valve should open with an audible click. When engine speed exceeds 1050 rpm, the control unit opens the circuit and the valve closes. The second Idle Speed Boost Valve on cars with air conditioning is switched on and off at the same time as the air conditioning compressor by the A/C relay.