Anti-Afterburn System

Fig. 96 Anti-Afterburn Control Solenoid Valve:

Fig. 53 Anti-Afterburn System Diagram:

The anti-afterburn valve senses the change in intake manifold vacuum during gear shifting or deceleration, and supplies fresh air into the intake manifold in order to prevent the dumping of excessive quantities of fuel.
When manifold vacuum suddenly increases, such as during deceleration, the diaphragm in the valve unit opens the valve. Air flow from the air chamber to the sensing chamber is restricted by an orifice, creating a temporary pressure differential on the diaphragm, which holds the valve open. The unbalanced condition lasts for a few seconds until the pressure in both chambers is equalized, then the spring pushes the diaphragm up, closing the valve.
The anti-afterburn control solenoid valve is provided to control the operation of the anti-afterburn valve by introducing manifold vacuum to hold the valve closed. When the engine coolant temperature is below the set temperature of the thermosensor, and vehicle speed is below the preset value of the control unit (for manual transmission cars), or the shift lever position switch is in the Neutral or Park position (for automatic transmission cars), the anti-afterburn control solenoid valve is activated to open the vacuum passage, but the valve will not open because there is no vacuum difference on the diaphragm.