Idle Speed/Throttle Actuator - Electronic: Description and Operation

Fig. 1 Idle Control System (A/T only):

This system maintains a stable idle speed under different engine loads. Idle control is accomplished using two throttle controllers, the idle boost throttle controller (with A/C, this controller has a dual diaphragm) and the throttle controller. The solenoid valve control unit monitors the inputs and directs voltage to the three solenoid valves:

1. The idle boost solenoid valve is energized:
When the transmission is in gear or the air temperature is below 19°C (66°F), Applying vacuum to the idle boost throttle controller.

2. The A/C idle boost solenoid valve is energized:
When the A/C compressor is energized, applying vacuum to the outer diaphragm of the idle boost throttle controller.

3. The frequency solenoid valve C is energized:
When the engine speed is above or below 730 rpm or the engine coolant temperature is above 60°C (140°F).