Deceleration Control System: Description

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

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

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