Deceleration Control System: Description

Deceleration systems reduce HC emissions through the use of an air switching valve, coasting air valve, dashpot (all Man. Trans. models except Federal trucks) and a deceleration spark advance system consisting of an engine speed sensor and solenoid valve.

Air switching valve cuts off fuel to by-pass holes and pilot outlet by supplying additional air to slow idle passage. Coasting air valve supplies additional air to intake manifold. Deceleration spark advance system advances ignition timing, which is usually controlled by carburetor ported vacuum and engine speed.