DECEL Throttle Modulator: Operation

Manifold vacuum is routed through a PVS valve and a solenoid vacuum valve, which is normally closed, to the vacuum throttle modulator. Power is available to solenoid vacuum valve through an electronic sensor, but the sensor ground circuit is 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 to allow vacuum to reach solenoid vacuum valve.