G 30 Van V8-454 7.4L VIN N TBI (1995)
Engine Speed Governor System: Description and Operation
ISC System
DESCRIPTION
The idle speed control actuator system assists the idle air control system in controlling the idle speed, primarily at cold temperatures. The idle
speed control actuator is a vacuum operated device which opens the throttle slightly (2 to 3 degrees of angle) to increase the cold engine idle
speed, to improve the mixing of the air and fuel, and to allow lower warmed up engine idle speeds. The idle speed control actuator is controlled by
the idle speed control actuator solenoid, which is controlled by the control module.
OPERATION
To increase the idle speed, the solenoid is turned "OFF," and no vacuum is routed to the idle speed control actuator, allowing it to open the throttle
slightly. To decrease the idle speed, the solenoid is turned "ON" and vacuum is routed through the solenoid to the idle speed control actuator,
allowing the throttle to fully close.
In conjunction with the idle speed control actuator system, the idle air control continuously monitors and controls the engine idle speed to the
desired idle speed. A Tech 1 scan tool will read the control module commands to the idle speed control actuator system.
