Vacuum Control Valve (VCV)

A 2-port valve may be in open or closed position when engine is cold, but should reverse when engine is warmed to operating temperature.
For 3-port valves, passage "A" to "B" should be closed and passage "A" to "C" should be open with a cold engine. See Fig 1. With engine at normal operating temperature, VCV should be open between "A" and "B" and closed between "A" and "C".
For 4-port valve, check "A1" to "B1" and "A2" to "B2" separately. See Fig 1. A 4-port valve may be in open or closed position when engine is cold, but should reverse when engine is warmed to operating temperature. If these conditions are not met, replace valve.

Fig 1: Identifying Vacuum Control Valves