Idle Speed Control Unit

The idle speed control unit processes the following information: engine speed signal (ignition terminal TD), coolant temperature, idle speed signal (throttle valve switch), vehicle speed signal (speedometer), automatic transmission shift lever position and A/C compressor cut-in signal.

At idle speed with the vehicle stationary (speed signal zero), the idle speed control unit scans the momentary input signals. From these signals, the microprocessor calculates the mean airflow volume and adjusts the control current to the idle speed air valve accordingly. In addition, the total control range is readjusted to the new control current so that the maximun control range is available when the engine load is increased.