DECEL Throttle Modulator: Operation

Manifold vacuum is routed through a Ported Vacuum Switch (PVS) and a solenoid vacuum valve. The solenoid vacuum valve is normally closed to the vacuum throttle modulator. Power is available to solenoid vacuum valve through an electronic sensor. Electronic sensor ground circuit is normally open. As engine reaches 1850 RPM, ground circuit in sensor is completed allowing solenoid vacuum valve to open. Vacuum pulls throttle modulator diaphragm which pushes throttle to high idle position during deceleration. Engine coolant must be above 125°F before PVS will allow vacuum to reach solenoid vacuum valve.