Idle Up Control Valve: Description and Operation

Fig. 5 Idle Speed Boost:

The idle speed boost system will maintain engine idle speed within a 200 rpm range despite varying engine loads. The system uses an electrically operated air bypass valve similar to the air conditioning idle air bypass valve. The valve is operated by a solid state relay which measures engine speed. If the engine speed drops below 750 rpm, the relay opens the valve and allows a small amount of metered air to bypass the throttle plates. This additional air will stabilize the engine idle. When the speed rises above 1050 rpm, the relay switches the valve closed.