Hard to see what it is. What application is it in. Is that a vacuum nipple? Couple be a map sensor or something. Is that and the wires coming off the only fun bits?

 

I really have no idea, its just hanging there by a couple of wires on the drivers side towards the firewall. I haven't traced the wires yet, i honestly just noticed the thing. It COULD be a vaccuum nipple but it's awful short (1/4 of an inch). Here's a couple more pics.

 

When you push on that nipple, does it move? What year truck?

 

Does not move. 1987 f150.

 

Might try posting a picture in the bricknose section and see if those guys are familiar with it. Now, the bottom of that, does it look like a female electrical terminal, like what might go on, say, an oil sender?