I have a 93 f350 460 5 speed.
Trying to find out where this vacuum hose goes and what it does.

I also have a spark plug that's really tight and doesn't want to come out. It moves a bit of I use a lot of force but it won't come loose. I just sprayed some wd 40 on it but looking for options on how to get it out. Thanks

 

No idea on the hose.. But for the plug depending on location. Try getting some heat to it maybe a small butane torch. Obviously clear anything out that's at risk for burning, then take some pliers and an ice cube the the plug. This will cool it and hopefully break free whatever's holding it in, unless it is cross threaded in that case you'll need to drill it out tap it and put a helicoil in, also not a hard task given you have access to the hole.

 

That hose goes to the lower canister.
Is the lower canister missing?

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Yes the lower canister might be missing. What does it look like. Just a cylindrical can? How many lines are supposed to go to it?
Also what would this affect of its not hooked up? Thanks

 

It only has the one hose going to it like in the diagram above.
You can see the lower canister in the photo below:


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I think I have the lower canister as that line in my photo is connected to it. Just don't know where it's supposed to go from there? It looks like it goes under the engine somewhere?
What does it do if not connected? Vacuum leak?

 

Is this the same hose in the photo?
If not then then hose more than likely goes to the muffler on the fender.



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Yes it's the same hose. It's not very long so I don't think it can go too far. Which muffler on the fender are you talking about?

 

Being the same hose then it should go to the lower canister.
The muffler on the fender is the dump muffler for the Secondary Air Injection (AIR) System.

 

I have a 94 and 96. One side of the canister has a breather cap, the other has a "F" fitting with a vacuum hose and a larger hose. The larger hose goes under the canister and attaches to a metal line that runs along the frame rail. Crawl underneath and look for a metal line along the top of the frame rail, may be the same for a 93.