Throttle Return Control System: Operation

Manifold vacuum is routed through the solenoid vacuum valve, which is normally closed, to the throttle lever actuator. Upon vehicle deceleration, electronic speed sensor signals solenoid vacuum valve to open when engine speed is above a preset RPM. When valve opens, manifold vacuum is directed to throttle lever actuator, which extends to open throttle slightly. When engine speed drops below the preset RPM, solenoid valve closes, retracting throttle lever actuator and returning throttle to curb idle position.