Hi guys, I would love it if someone could respond to this ASAP.
I have a 2004 F-150 Lariat with a 5.4L V8, and I'm trying to get it road-ready. I've been riding in with a misfire in cylinder 8 for a while because I haven't had the time to get it fixed (by a while I mean like 10 months...I know, it's bad), because I'm a part-time student and I'm at college part-time, so going a day without my truck puts my schedule behind. By the way, I do keep up with maintenance with my truck like oil change, transmission fluid, etc... My question is what I would need to do so it can be ready to travel from home and college (a 5-hour drive). I got the transmission rebuilt already, and now it's just engine work. I'm just trying to save money by not having to buy a new car or truck, and on top of that, the truck belonged to my grandpa, and it was given to me because I love that truck, and I don't want to let it go.
Like I said, any suggestion would help. Thanks a lot

 

First, welcome as this is your first post.
There are a lot of variables to working on any vehicle (especially these Trucks) & yes, 10 months is REALLY bad to let that go.
With that being said, your $0 cost diag options should start with a visual inspection & progress to more invasive as needed.
You will want to unplug the #8 coil (be careful with the plastic / clips as they are old & brittle) then unbolt the little 7 or 8mm bolt that holds it down.
Pull the coil, boot & spring & look for signs of arching or cracks or if it is a POS coil from eBay.
Only use original Motorcraft parts to replace these.
If you don't see anything, look down in the well for any moisture / liquid.
The back coils "can" get dripped on during rains from the cowl above & cause shorts / misfires.
If you still don't see anything then swap the coil with the next cylinder & see if the misfire "moves" with it.
If it moves, you have an issue with the coil or boot or spring.
If it doesn't move, you likely have an issue with the spark plug.
At that point it is still possible you could have an issue with the wire harness or ECU but those are less likely.

If you find it is with the plug then you will have to remove the plug to inspect.
You didn't mention if this is the 5.4L 2v or 3v & they both have their own issues with plugs.

2v - most common issue is an improperly torqued plug that has loosened up & backed out.
Proper torque on these is CRITICAL!

3v - most common issue is the electrode strap has broken off & been shot out the exhaust valve.
*** WARNING: it is VERY common for these plugs to get stuck in the head & end up broken off when you try to remove it.
If you are a descent mechanic, this is not the end of the world, just a giant P.I.T.A.
You mentioned you don't have much time & can't be without the truck.... You should find a mechanic that is familiar with broken spark plugs & has the proper special tools to deal with it.

As a side note you have likely done permanent damage to your catalytic converters.
Long-term misfires are the most common way to kill a converter on these trucks.
If it gets to this point, you will need to save a bunch of pennies & I hope you don't live in CA or NY or it will cost you at least 3x more pennies than a sane state would.
Flowmaster makes bolt-on replacement converters that are good quality & far less than OE (if they even still make them).

 

Thx i for all the information, and it was the sparkplugs, and as soon as I changed them..a couple of days later my check engine light came back on for my cat lol...but once again I appreciate it.

 

you got the cat code due to letting the mis-fire go so long, it sent unburnt fuel into the cat... not good.

 

Try a additive called cat clean, any big 3 parts stores have it, even wally world, see if your cat code goes away, before sinking $3-500 in new ones. Its only going to get worse, and you'll be back with no power on take off, question.