What is this part?

[mcfearin]

There is a long torpedo like canister on the fire block to the passenger side of my engine. It has a thine tube coming out of it but the tube is cut off and has a screw run into the end, some back yard fix some mechanic did at some point I guess. I have no idea what the part is so I can't replace it.
1992 Ford Explorer XLT

 

[awood]

Sounds like the "Vacuum Accumulator". I'm not sure what Ford calls it. If that's what it is, it's a vacuum chamber that provides enough instant vacuum to move the actuators for your climate control system (Hot/Cold blend door, and Defrost/Floor, etc). Without it, I suspect those actuators would move very slowly until the tiny vacuum lines can provide enough vacuum to move the big diaphragms on the actuators - if, in this case, they are actually hooked up!!!