I just stumbled through replacing the starter on 2005 Accord. Pulled off intake manifold, replaced starter, put it all back together. Now I see this connection below the air intake hose (which I also replaced). I don’t remember removing a hose from this port, and don’t see any dangling hoses. What did I miss? Is this a vacuum line or coolant line? What connects here? The car seems to run fine, but looks like something was here?.

 

Is your car manual or automatic transmission?
4-cyl or V-6 engine?
Back up a bit with the camera, I can't tell what's what. Is that the air filter box over on the right side of the photo?

 

It is a manual xmission. That is the air filter on the right and the air intake hose to the intake manifold. I will get a wider angle picture.

 

That's a vent for the transmission. It would have had a rubber cap (#2 in the picture) to keep stuff from falling into the tube.
The cap is part # 21396-P20-000 for about $5 or $6 from a Honda dealer.

 

Thank you so much. I think I have the cap. I found a little rubber do-dad after cleaning up the garage, and thought it was something from another project.

 

It should have a hole pointing the way it goes in the picture. If you find something that caps it off airtight, that's not the right thing.