This used to pop up on here all the time. The white vacuum hose under the dash for the recirculate vacuum actuator falls off. Just push it back on. If its on there, you have a leak somewhere in your vacuum supply hoses (possibly a reservoir too, but not likely).
RIP '94 Amber Fire Pearl Metallic Thunderbird on Bullitts [email protected]
96 Sport '02 Explorer PI with ported heads, 90MM LMAF, DirtyDog Marauder TC, Lasota tune, Jmod, Magnaflow mid-mount with X, no cats. Urethane drivers motor mount. HIDs!