Engine Control Module: Description and Operation

Deceleration Control System:

The deceleration control system controls the air/fuel mixture and advances the ignition timing to reduce CO and HC emissions, to reduce fuel consumption, and to prevent the front catalytic converter from overheating.
The system comprises the slow fuel cut solenoid valve, coaster richer solenoid valve, vacuum solenoid valve, dashpot, and mixture control valve.
The slow fuel cut solenoid valve closes the primary slow fuel passage on command from the engine control unit. The coasting richer solenoid valve supplies extra air/fuel mixture to add to the primary slow fuel on command from the engine control unit. The vacuum solenoid valve applies intake manifold vacuum to the vacuum control unit of the distributor on command from the engine control unit. The mixture control valve supplies air into the intake manifold during the first period of deceleration. The dashpot commands the throttle valve to close gradually.