Deceleration Control System: Operation
The manifold vacuum is routed through the solenoid vacuum valve to the vacuum throttle positioner (modulator). The solenoid vacuum valve is normally in the closed position.
Power is available to the solenoid vacuum valve through an electronic sensor, but the sensor ground circuit is open. When the engine speed is greater than the predetermined RPM setting, a signal is sent to the solenoid, which allows the manifold vacuum to activate the throttle positioner.
NOTE:
On some models, the vacuum switch notifies a sensor when the manifold vacuum reaches a predetermined value. The sensor then signals a solenoid to activate the throttle positioner (modulator).
The vacuum pulls the throttle positioner diaphragm, which pushes the throttle to the high idle position, during deceleration.