Air Valves

There are two types of non-ECM controlled air valves that are used on some engines to perform cold fast-idle control. The first type simply uses a thermo-wax element to vary the amount of bypass air based on the coolant temperature. Once the engine reaches operating temperature, the air valve should be fully closed.

Bi-Metal Air Valve Air Valve

The second type uses a spring loaded gate balanced against a bi-metal element. As engine temperature rises, the bi-metal element deflects to close the gate valve, thereby reducing the amount of bypass air. A heater coil surrounds the bi-metal element and is used to heat the element whenever the engine is running (fuel pump operates). An air valve quick check can be performed by pinching off the supply hose and observing rpm drop. The drop should be less than 50 rpm when the engine is warm, and should be significantly higher when the engine is cold.

From Air Clee

From Air Clee

Throttle Valve

To Air Intake

Throttle Valve

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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