Idle Control System

IDLE CONTROL SYSTEM
The idle speed is controlled by the ECU and various solenoid valves such as idle control, fast idle, A/T idle control, and A/C idle boost solenoid valves. These change the amount of air bypassing into the air intake manifold.
The A/C idle boost solenoid valve opens the A/C idle boost valve to increase the air flow when the air conditioner is turned on.

Idle Control Solenoid Valve
When the idle speed is reduced due to electrical, or other, loads on the engine, the valve opens to bypass additional air into the intake manifold. This additional air will allow the idle speed to increase to its normal speed (750 ± 50 rpm). The operation depends upon changes in the voltage at the FR terminal of the alternator for quick response. The valve also lowers the fast idle speed during warm-up, after the coolant temperature has reached 40°C (104°F). To prevent erratic running after the engine first fires, the valve is opened during cranking and immediately after starting to provide additional air into the intake manifold.

Fast Idle Control Solenoid Valve
To prevent erratic running when the engine is cold, a higher idle speed is needed. When the engine is cold, the valve opens to bypass additional air into the intake manifold. This operation is dependent upon coolant temperature and atmospheric pressure. The valve is open below -15°C (5°F) or (below 40°C (104°F) at high altitude).

A/T Idle Control Solenoid Valve
With the A/T shift lever is in gear, the idle speed will ten to lower. To compensate for this, the valve opens to maintain the specified idle speed (750 ± 50 rpm).

A/C Idle Boost Solenoid Valve
When the air conditioner compressor is on, the A/C idle boost solenoid valve is energized, the A/C idle boost valve opens to increase the air flow, and the idle speed is maintained at 750 ± 50 rpm. Adjust idle rpm with the A/C idle boost valve adjusting bolt.