Deceleration Mode

When the driver releases the accelerator pedal, the air flow into the engine is reduced. The corresponding changes in the throttle position and the manifold air pressure are relayed to the Control Module, which reduces the injector pulse width, in order to reduce the fuel flow. If the decel is very rapid, or for long periods (such as long closed throttle coast-down), the Control Module shuts OFF the fuel completely in order to protect the Catalytic Converter.