Eclipse L4-1795cc 1.8L SOHC (1990)
Idle Air Control Motor (Stepper Motor): Description and Operation
Idle Speed Control Servo (ISC Stepper Motor)
Idle Speed Control (ISC) Servo Circuit
The ISC servo, located on the throttle chamber, consists of a motor, worm gear, worm wheel and plunger. A motor position sensor (MPS) is used to
detect plunger position, and an idle switch is used to detect idle position. The worm wheel (attached to the motor shaft) is meshed with the worm gear on
the plunger. As the motor rotates, according to the signal from the ECU, the plunger extends or retracts. This actuates the throttle valve via the ISC
lever. In this way, the idle speed is controlled by changing the throttle valve opening.