Century V6-173 2.8L VIN W FI (1987)
Engine Control Module: Description and Operation
Deceleration Mode
When the driver releases the accelerator pedal, air flow into the engine is reduced. The corresponding changes in throttle position and manifold air
pressure are relayed to the Electronic Control Module (ECM), which reduces the injector pulse width, to reduce fuel flow. If the deceleration is very
rapid, or for long periods (such as long closed throttle coast-down), the ECM shuts fuel completely "OFF," to protect the catalytic converter.