Deceleration Valve: Description and Operation

Mixture Control Valve:

The mixture control valve supplies fresh filtered air from the air cleaner to the intake manifold during deceleration, to prevent over enrichment of the air/fuel mixture and after burning in the exhaust manifold. The valve has a diaphragm, and two chambers (one on either side of the diaphragm) joined by a small orifice. The valve is controlled by manifold vacuum. When the throttle is closed suddenly, manifold vacuum increases rapidly in one chamber and the diaphragm opens the valve, allowing fresh air into the manifold. After a short time the pressure on either side of the diaphragm is equalized through the orifice, and a spring pushes the diaphragm back, closing the valve passage to the intake manifold.