Mixture Control Solenoid: Description and Operation

Fig. 37 Mixture control valve operation. Shown at constant RPM:

Fig. 38 Mixture control valve operation. Shown during deceleration:

The mixture control valve is controlled by intake manifold vacuum applied to an upper and lower chamber, Figs. 37 and 38. The valve allows fresh air to pass into the intake manifold during sudden high vacuum operation.

At constant RPM, the vacuum signal to both chambers A and B, of the mixture control valve is stabilized. On sudden deceleration, the vacuum signal applied to the upper chamber through a calibrated opening is weaker than the direct signal applied to the lower chamber. This difference allows the valve to open and fresh air is routed to the intake manifold. After a few seconds, the vacuum in the two chambers stabilizes through the balancing port, and the mixture control valve closes.