We took our 1990 Ford F-150 with fuel injected v8 engine to the local repair shop for an oil change. When we got it back, it was running rough. When we looked under the hood, we found a mysterious cylindrical part with a hose on just one side and a disconnected hose. Strangely, the hose doesn't seem to reach the part with the opening and the hose is nice and shiny on the end. It's a 30 year old truck and under the hood, this is the only shiny thing you'll find. Based on diagrams I've seen online, this might be a themactor dump silencer or a check valve. Maybe it's neither. I'd welcome any input on what the hose should connect to - and how.

 

The larger canister is the air pump intake, and the hose may have been clipped down, but should remain open.
The smaller canister is the silencer, for when the air is being bypassed out of the system.

 

Thanks! This was really helpful.