Fast Idle Valve

Description
To prevent erratic running when the engine is warming up, it is necessary to raise the idle speed. The fast idle air bypass valve is controlled by a thermowax plunger. When the engine is cold, the engine coolant surrounding the thermowax contracts the plunger, allowing additional air to be bypassed into the intake manifold so that the engine idles faster. When the engine reaches operating temperature, the valve closes, reducing the amount of air bypassing into the manifold.

Inspection
NOTE: The fast idle valve is factory adjusted; it should not be disassembled.
1 . Remove the intake air duct from the throttle body.
2. Start the engine.
3. Put your finger over the lower port in throttle body and make sure that there is air flow with the engine cold (coolant temperature below 30°C, 86°F).

•   If not, replace the fast idle valve and retest.

4. Warm up the engine (cooling fan comes on).

5. Check that the valve is completely closed. If not, air suction can be felt at the lower port in the throttle body.
•   If any suction is felt, the valve is leaking.
Replace the fast idle valve and recheck.