Seville V8-300 4.9L (1991)
Idle Speed Control Motor: Description and Operation
Idle Speed Control (ISC) Motor
Throttle Body Assembly - Exploded View
The Idle Speed Control (ISC) Motor is mounted on the throttle body and is used to control engine idle speed. The ISC plunger acts as a moveable
throttle stop changing the primary throttle valve angle. The ECM/PCM monitors engine idle speed and moves the ISC plunger (throttle stop) to maintain
the desired idle speed required for the operating condition.
An integral part of the ISC is the throttle switch. The position of the throttle switch determines whether or not the ISC controls idle. When the throttle
lever rests against the ISC plunger, the switch contacts are closed and the ECM/PCM moves the ISC plunger to the programmed idle speed position.
When the throttle lever breaks contact with the ISC plunger, the switch contacts open and the ECM/PCM stops sending idle speed commands. Engine
speed is again controlled by the accelerator pedal.