What Is It?

Air Pump Valve

> On the passenger side of the engine, there is a "valve"? that has a line
> coming in from the smog pump (I think) and going out to the underside of
> the air filter box. Off the top of this "valve" there is an elbow with a
> 2ft. vaccum line attached. Where exactly does the other end connect to? I
> am about to install a new mass air sensor and would like to attach this
> before I button everything up. If it goes to the throttle body, Where
> exactly does it connect? I can't find anywhere it could attach to.
> BTW, the car is an '87 s4

The valve in question is the air pump diverter valve, commonly called the "gulp" valve. It diverts pump output to the air cleaner during high vacuum conditions such as deceleration. The top line goes to manifold vacuum at the tee fitting near the brake booster.
John Kunkel

On my 86 the vacuum line leads to a port on the front of the throttle body. There are actually two ports there. The one on the driver side is for California cars and the one on the passenger side is for everyone else. Whichever you have, the other one will be covered by a red rubber cap. FYI -- my rubber elbow at the throttle body was swollen and needed replacing as well as the rubber cap.

Douglas Hampton