I'm guessing this is a vacuum line that's been capped off. Any idea what it goes to and if it's a problem? I bought 20' of vacuum line to re-run everything. Just wondering why it's like this.

 

I believe that is the iac. EDIT: It's not the iac I was completely off

http://www.fullsizebronco.com/forum/...ge=1&_k=acdcg3

This is a great link showing how to reroute/replace vacuum lines for our motors

 

That looks like it runs to the canister behind the passenger side headlight. Where it connected to by the throttle body is the purge solenoid. I can get pics from my engine later today if you would like

 

If you have time that'd be great. I plan to fix it Sunday when I do the full tune-up.

I feel stupid about how the vacuum system works and what exactly it does.

I just looked at my canister and it has no ports to hook vacuum lines to. It just has a pair of wires coming out of it.

 

This is the canister purge solenoid where the one end of your line is connected
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On my 95 5.0 this is the canister mounted below the battery between the frame and radiator. The smaller black line is where the line comes from the purge solenoid.
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Im off my cell phone right now and am hoping the inserts the whole pictur. Bur if you look above the altenator the small black line is for the purge solenoid on my truck. I wish i could highlight the l whole line to make it easier to see. But in the bottom left of the pic you can see the canister where it runs to and can follow that up pretty well to see how its ran
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That is the purge valve line. Excess gas fumes from fuel in the gas tank goes to the charcoal filter (black box in the pictures above). When the engine is operating at a temp and rpm that it won't be interfered with, the purge valve opens and allows the engine to suck all the built up fume residue out of the charcoal canister so it doesn't get overloaded.
It's not emissions, it's disposal of excess gas fumes.
It should be functioning for (obvious) safety reasons.

 

Looks like the vapor canister needs replacing. The top is rotted out. I guess that's why they pulled it and capped it since it wasn't working anyway.

Does that other line going into it run all the way from the gas tank?

Vapor canister rotted out

 

I personally do not know where the other line runs to. The gas tank would be my best guess like you said though. That vapor canister definately is not doing its job. I dont think ive seen one deteriorate like that.