Went to go replace the valve cover gasket today and found a plug that wasn't connected to anything nor can I find where it "might" go.

Here is a pic of said plug.




Its the black one to the left of the red wire on the second pic. It runs the pass side above the fuel rail and intake w/ 2 other single wire connectors.

 

What are the wire colors?
What are we working on? (year, engine size)

 

It looks kinda like a EGR control valve connector but it maybe unused and have no place to connect to.

The "red wire" is a vacuum line and needs to be connected to its port. Did you unplug it while working or did you find it just laying there?

If you can't find anyplace to connect the vacuum line just plug it with a small bolt for now.

 

Wire has tape and a loom but I think I see grey and brown (maybe?)

Yeah I'm bad about info, 90 F150 4.9l

I didn't unplug it so no clue where it leads. Everything else is acounted for that has been disconnected.

 

I just changed the passenger side valve cover gasket today. What a pain. It was tough keeping all those plugs and cords and crap out of the way. That looks like the same plug that was in the same assembly as the coil and some other plugs i have no idea what for. The one i had like that plugged into a port right next to a gray one. Thats all i remember.

Probably not much help, but i wanted to share.

 

On my 5.8 there are a bunch of unused on the drivers side. I know 1 is for AC caus I dont have it, if it runs fine and you didnt unplug it I wouldnt worry about it.

 

just an extra plug, mine is like that as well. me thinks it may be for the injector cooling fan installed on some early efi 300s.

 

I think it goes to the "Injector Blower Relay" and the wire colors are more than likely Gray with a yellow stripe and Yellow with a blue stripe, with age the Yellow would look Brown.
It does not sound like you have this accessory.

 

Do you have a working canister purge valve? It uses a connector very similar to that one pictured, and the purge valve usually sits between two of the intake runners.

 

I also have a 1990 4.9. Got bundled up and went out to have a look. It is still 28 deg here so I didn't spend a long time looking.
Since it looks like you have the upper plenum off and the connector is on the passenger side close to the injectors, I looked there only.
The red "wire" is a vacuum line. One end connects to the vacuum tree coming off the upper plenum, and the other end connects to the fuel pressure valve located on the fuel rail.
The connector goes one of two places. There are no extras visible on my truck. The first spot is the air temp sensor located just behind the alternator on the lower plenum.
The second possibility is the water temp sensor used by the computer. It is located between the alternator and the upper radiator hose. The wire colors for the water temp sensor are green/red stripe I think.
Can't tell what color the wires are on the air charge temp sensor. Not much wire showing, and it is dirty and not easily reached to clean.
If the wires on your connection are pretty long, they may reach somewhere else that I didn't look. Be glad to look some more if this doesn't get r done.
If you need pics holler.
Good luck Frank