Vacuum Delay Valve
WARNING: This page is about a different car, the 1995 Ford Pickup, 1995 Ford F-Super Duty, and 1995 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Vacuum delay valve is inserted in vacuum lines to provide gradual application or vacuum release to engine or emission control devices. One-way or 2-way valve may be used, depending on function and system.