Idle Speed/Throttle Actuator - Mechanical: Description and Operation

Fig. 21 Throttle Positioner System:

Fig. 22 TP System Operations Schematic:

The Throttle Positioner holds the throttle valve open slightly on deceleration for more complete combustion. HC and CO are reduced by preventing the throttle valve from closing suddenly. The Throttle Positioner is vacuum actuated and controlled by a vacuum switching valve (VSV).

Fig. 23 TP System Operations Chart:

The VSV receives input signals from the electronic control unit (ECU) based on engine rpm and throttle position.