Comanche 2WD L4-150 2.5L VIN E TBI (1989)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
ISA Motor/Closed Throttle Switch
This component is used to control the idle speed and the throttle stop angle (deceleration). The throttle lever rests on the adjustment screw of the ISA
motor, and its position is changed, under certain conditions, when the ISA plunger extends and/or retracts. The ECU sends current to the ISA motor to
extend or retract the plunger depending on the current operating conditions. The ECU uses information it receives from its input sensors to determine
when and what polarity of current it should send to the ISA motor.
The ECU controls the ISA motor by changing the polarity or cutting off the current that is sent to it, and it also uses the B+ Latch Relay to apply current
after the engine has been shut off. It does this so that the ISA motor will extend the plunger for the next start up. When the engine is restarted, it will
operate at a fast RPM until appropriate input sensors indicate to the ECU that the idle can be returned to a curb idle RPM. The ECU will then retract the
ISA plunger until the idle comes down to a programmed RPM for the current driving conditions.
