Civic Hatchback L4-1488cc 1.5L SOHC (D15A2) 3V Carb (1987)
A/C Idle Boost Throttle Controller: Description and Operation
Fast Idle Mechanism
Fig. 9 Typical fast idle mechanism
The air bypass valve is controlled by a thermowax plunger, Fig. 9. When the thermowax is cold, the valve is open. When the thermowax is heated, the
valve is closed. When the engine is cold the valve allows additional air to bypass into the intake manifold so that engine idles faster than normal. When
engine reaches normal operating temperature, the valve begins to close, reducing amount of air bypassing into the intake manifold.