Except Federal Models
The vacuum switching valve (VSV) has 3 ports, 2 of which are opened or closed by a solenoid plunger. Solenoid plunger is energized when coolant temperature is under 122°F (50°C) or for 10 seconds after WOT switch is turned on (coolant temperature over 122°F).
The VSV reverses the application of manifold vacuum to the air switching valve. When energized, the VSV connects chamber "B" of air switching valve to intake manifold. When plunger is de-energized, it plugs chamber "B" and connects chamber "A" of air switching valve to intake manifold.