Vacuum Vent Valve
WARNING: This page is about a different car, the 1995 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
Vacuum vent valve controls induction of fresh air into system, preventing accumulation of fuel vapors which could cause decay of vacuum diaphragms. Valve may be vent only or combined vent and delay valve. Valve should always be mounted with ports pointing downward.