Deceleration Control System: Operation
Manifold vacuum is routed through solenoid vacuum valve, which is normally closed, to vacuum throttle positioner (modulator).
Fig 1: Schematic of Ford Decel Throttle Control System Components indicated with dotted lines may not be found on all models.
Power is available to solenoid vacuum valve through an electronic sensor, but sensor ground circuit is open. When engine speed is higher than predetermined RPM setting, signal is sent to solenoid, which allows manifold vacuum to activate throttle positioner.
NOTE:
On some models vacuum switch notifies sensor when manifold vacuum reaches predetermined value. Sensor then signals solenoid to activate throttle positioner (modulator).
Vacuum pulls throttle positioner diaphragm, which pushes throttle to high idle position during deceleration.