As I was finishing changing the spark plugs on my 2004 F150 5.4, i noticed this wire and switch/button hanging with no obvious place to go. See pics. Where does it go?

Thanks!!!!!

 

It's a vacuum line. Maybe hooks to base of throttle body or intake manifold. The disc at the end of it looks like half of a check valve. If so, it's broke.

 

That looks like the vacuum line for IWE system for 4WD... if you have 2WD they cap it off and it doesn't connect to anything. Just lays around the engine compartment.

 

I just went out and looked at my 2006. I don't have this same vacuum line but there is one similar that hooks to something between the battery and the firewall. See if you have something there to hook it to. While I was looking at mine I discovered a gray vacuum line that's broken. If you see one of these let me know where it goes! LOL!

 

At this video you will see your red vacuum line at 50 seconds:

 

So since I have 2wd, this valve is unnecessary. That's great. I appreciated everyone's help

 

Just to make sure you should start your truck and see if there's vacuum at the red vacuum line. If so, then it goes somewhere.

 

 

If your truck is 2wd, ignore it.