Electronic Idle Speed Control
WARNING: This page is about a different car, the 1984 Volvo 760, 1984 Volvo 245, 1984 Volvo 244, and 1984 Volvo 242. However, it is still accessible from the selected car via links, so may be relevant.
This system maintains a constant idle speed by varying the amount of air by-passing the throttle valve. This air is controlled by the air control valve.
The air control valve is operated by the electronic idle speed control unit which receives engine information from the throttle switch, coolant temperature sensor, and the ignition coil.