Constant Idle Speed (Cis) System
CIS system is incorporated into LH-Jetronic fuel system. Its main function is to control engine at idle or near idle by regulating air control valve. Combined information from throttle switch, engine speed sensor and coolant temperature sensor, is processed through fuel system ECU to operate air control valve.
Air control valve increases or decreases amount of air which is taken from in front of throttle valve, by-passed around throttle valve, and injected into intake manifold (behind throttle valve). It consists of a small electric motor, mounted between connecting hoses at air flow throttle valve. Electric motor rotates clockwise or counterclockwise, depending on electrical signals received from ECU. See Fig 1 .