Idle Control System

The curb and fast idle speeds of the engine are controlled by the electronic idle control valve and the fast idle bypass valve, in response to various signal inputs within the system (A/C signal, Starter signal, etc.)

Electronic Idle Control Valve (EICV)

The EICV changes the amount of air bypassing into the intake manifold in response to electrical signals sent from the ECU. When the valve is activated, it opens to maintain proper idle speed. After the engine is started, the amount of air is increased to raise the idle speed accordingly. When coolant temperature is low, the amount of bypassed air is directly proportional to coolant temperature. When coolant temperature is below approximately 86°F, the EICV activates the fast idle bypass valve to prevent significant drops in idle speed.

Electronic Air Control Valve (EACV)

The EACV is used on 1988 models and performs the same function as the EICV in previous models.

Fast Idle Bypass Valve

The air bypass valve is controlled by a thermowax plunger. 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 the amount of air bypassing into the intake manifold.