Idle Speed/Throttle Actuator - Mechanical: Description and Operation

Fig. 22 TP System Operations Schematic:

Fig. 23 TP System Operations Chart:

The Throttle Positioner, located on the carburetor, 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). The VSV receives input signals from the Electronic Control Unit (ECU) based on engine rpm and throttle position. Diagnosis and testing of the ECU and VSV is found in COMPUTERIZED ENGINE CONTROLS.