Deceleration Mixture Control System

During rapid deceleration when throttle is closed and intake manifold vacuum is high, excessive fuel may be drawn into intake manifold. Due to the lack of air (throttle closed), this causes high levels of HC and CO emissions. Some of this is rectified using the fuel-cut system; however, some unnecessary fuel is still drawn into intake manifold. The deceleration mixture control system is designed to draw additional air into the intake manifold during deceleration. This provides adequate air for burning of the extra fuel.

Deceleration mixture control system consists of a mixture control valve, one-way check valve, manifold vacuum signal hose and air delivery hose. The mixture control valve has a self-balancing vacuum diaphragm which does not allow the introduction of additional air during periods when manifold vacuum is constant. A rapid increase in manifold vacuum (such as that caused by heavy deceleration) is required to activate mixture control valve. One-way check valve is installed with Gray side toward mixture control valve.