DECEL Throttle Control System: Description

The decel throttle control (modulator) system keeps the throttle valves open slightly during sudden deceleration to help reduce hydrocarbon and carbon monoxide emissions.

System consists of a governor module or speed sensor, a ported vacuum switch (some models), solenoid vacuum valve, throttle positioner (modulator) on throttle linkage, and electrical wiring and vacuum hoses. See Figure.

Some systems also utilize a vacuum switch that notifies the module or speed sensor when manifold vacuum is at a predetermined level. The system is electrically connected to the ignition switch and to the "TACH" terminal of ignition coil.