Mixture Control System: Description
The 1974 mixture control system consists of a mixture control valve connected to intake manifold and to Vacuum Switching Valve (VSV). Mixture control valve is controlled by VSV, computer, and speed sensor. Valve allows fresh air to enter intake manifold during deceleration from high or intermediate speeds.
The 1977-79 system controls hydrocarbon (HC) and carbon monoxide (CO) emissions during sudden deceleration. This is accomplished through a mixture control valve which allows additional fresh air to enter intake manifold when sudden deceleration (closed throttle) occurs.