Electronic Throttle Actuator Control (TAC)

The electronic TAC is a DC motor controlled by the PCM (requires 2 wires). The gear ratio from the motor to the throttle plate shaft is 17:1. There are 2 designs for the TAC, parallel and in-series. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is integrated into the main housing. The in-series design has a separate motor housing. Two springs are used; one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle when no power is applied. The force of the plunger spring is 2 times stronger than the main spring. The default angle is usually set to result in a top vehicle speed of 48 km/h (30 mph). Typically this throttle angle is 7 to 8 degrees from the hard stop angle. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle. For additional information, refer to TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC) .