Description & Operation

The deceleration control system prevents vehicle dieseling at shutdown and exhaust system overheating during deceleration. This is achieved by blocking fuel flow in the primary slow fuel delivery circuit when vehicle is decelerating or ignition switch is in the "OFF" position. System consists of a deceleration fuel shutoff valve which is controlled by the ECA based upon sensor and switch input signals. Failure in the fuel shutoff circuit should set code 22.

Also considered a part of deceleration control system is the anti-afterburn valve (also referred to as an anti-backfire or gulp valve). During deceleration with throttle closed, anti-afterburn valve allows additional fresh air to be drawn into combustion chamber through the intake manifold. This provides adequate air to burn fuel already existing in the intake manifold and any fuel which may be drawn from metering circuits due to high intake manifold vacuum. This will prevent raw fuel from entering exhaust system and converter, where backfires or overheating could result.

DECELERATION INPUT SIGNALS

Component	Function
Neutral Switch	Detect in-gear condition
Clutch Switch	Detect clutch application
Brake Switch	Detect brake application
Idle Switch	Detect throttle opening
A/C Switch	Detect A/C on mode
MAP Sensor	Detect manifold vacuum
BP Switch	Detect barometric pressure

NOTE: Failure in ECA sensor and switch input circuits can cause malfunctioning of fuel shutoff valve. For complete testing of applicable sensor and switch input signals, see EFC SYSTEM article in the COMPUTERIZED ENGINE CONTROLS section.

Fig 1: Deceleration System Fuel Shutoff Valve

Courtesy of FORD MOTOR CO.