Auxiliary Air Valve (Idle Speed): Description and Operation

Throttle Body Assembly - VIN 6:

Purpose
The auxiliary air valve provides additional intake air around the throttle valve when the engine is cold. This raises the engine idle speed until the engine is warmed and the engine speed is brought back to normal idle speed.

Operation
The auxiliary air valve consists of thermo-wax, springs and a valve. When the engine is cold or coolant is lower than 60°C (140°F), the thermo-wax contracts. In this state, the valve opens by the spring force allowing the air to be drawn into the intake manifold. Thus the amount of intake air increases even when the throttle valve is at the idle position and the engine speed rises to the fast idle state which is higher than the idle speed.

As the engine is warmed up, the thermo-wax expands gradually, causing the piston to push down on the valve gradually, thus the amount of air passing through the air valve decreases which reduces the engine speed. When the engine coolant temperature reaches about 60°C (140°F), the valve is fully closed and the engine speed is back to normal idle speed.

Location:
Permanently attached to the side of the throttle body.