Idle-RPM Control System

An electronically governed idle rpm control valve keeps the idle speed stable under the various engine operating conditions. Measured intake air from the airflow meter bypasses the throttle plate through the idle rpm control valve and subsequently calls for additional fuel injection. The amount of bypass air is determined by a variable orifice of the valve.

The idle rpm ECU controls the orifice via the rpm signal generated from the starter ring teeth. The opening is enlarged or reduced by a solenoid according to operating conditions (e.g. engine friction, automatic in "DRIVE" or air conditioner "ON"). The system is calibrated to stabilize at 950 rpm below 114 °F (4500) coolant temperature and 700 rpm above 114 °F (4500). It operates with closed throttle only.

With air conditioning switched "ON" or at an ambient air temperature below 41°F (500) the system will stabilize at 850 rpm.

With an automatic transmission in "DRIVE" the system stabilizes at 700 rpm.