Cherokee 2WD L4-150 2.5L VIN P MFI (1991)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Automatic Idle Speed (AIS) Motor
The engine controller operates the Automatic Idle Speed (AIS) motor to maintain the proper idle speed for all operating conditions. Inputs from the
throttle position sensor, speed sensor, and coolant temperature sensor are used by the engine controller to calculate the proper idle speed. Various
switches (brake, neutral/safety) are also used to provide input for the idle speed.
The AIS varies the air portion of the air/fuel mixture in the air bypass passage of the throttle body. It does this by extending or retracting the AIS pintle
into the air bypass passage. The further the AIS pintle protrudes into this passage the slower the idle speed, and the less the AIS pintle protrudes the
greater the idle speed. The engine controller adjusts the pintle position to compensate for various engine loads and operating conditions. Deceleration
stall is also prevented by increasing the airflow when the throttle is closed suddenly. The AIS motor is mounted on the side of the throttle body. The
AIS motor is activated when the ignition switch is placed in the ON position.
