I have a '93 Xcab 4x4 v8

Now for the cause of my frustration.
I have had my truck since this past October (2011) and in the last few months the engine has started acting up but since I wasn't driving it too much I just ignored it because it was an intermittent problem. Well... now I'm driving it more and really like the truck, but get frustrated when it's not running right.

Maintenance I've taken care of since purchase:

Transmission flush
I did this immediately following the purchase at the recommendation of the mechanic who did my inspection. I took the truck on a road trip across the state that weekend and averaged 23mpg! My average mpg was ~18-19 for the next few months =)

New tires - 31x10.50x15 ATs
I had a tire blow and needed a new set immediately so I brought the blown tire w/wheel to Discount Tire. The shop guy told me this was the correct size for my truck after seeing the wheel w/blown tire I brought in, but it turns out they're a little too big and rub! I was a little pissed but whatever... they look good =) Originally, I was planning to lift the truck and stuff 33s on it, but unfortuately as luck would have it, I just needed tires immediately and settled for these ones. The tires I had on it before were 255/65/15 and I'm guessing the increase in tire size is partly to blame for my lowered gas mileage...?

New spark plug wires
I try to keep track of my mileage every month of so when I fill up just to maintain an idea of how much I'm spending on gas each month, and when I noticed significantly decreased gas mileage (averaging ~10-12mpg), I popped the hood to check cables, air filter, etc I saw the wire going to cylinder 5 had been melted in half, so it wasn't able to fire. I fixed the cables and while replacing them checked the spark plugs and noticed corrosion.

New spark plugs
I thought this would help improve my significantly lowered gas mileage along with the new wiring. Between this and the wiring there wasn't a significant improvement in mileage... ~2mpg.

Now that you've got the back story and the different things I've done, here's my problems I' unable to figure out.

Headlights
The right side went out and while replacing it I thought I'd replace both at the same time since I had no idea when they were replaced last. About 2 months after replacing them they stopped working! I checked to see if they were bad, but they're both fine. The part that confuses me is that my brights work if I hold the lever back, but immediately go out when I release it. I plugged in a new set of lights to see if they are just bad lights but they don't work either. The dash/running lights and turn signals all work fine though...
Any ideas on what's causing this? I'm not sure how to check the connections, so if that's the answer I'd appreciate someone explaining how to do this =)

Engine
This is the BIGGEST issue for me because it keeps the truck from running and me getting where I want to go on time!
With no rhyme or reason the engine will act like it's running out of gas. It starts stuttering, like it's not firing and then will die or other times it won't start but the starter will fire to the point my engine floods, if I wanted. If I try to give it gas when it's doing the stuttering it dies instantly. The 2 most common times it happens are when I'm starting up after a long drive or on hot days it will do this if it's been sitting or if I'm at a stop light or in bad traffic. My initial thought was maybe it was really running out of gas, but it's done this while on a full tank and close to empty with 1-3 gallons left in the tank. Now I'm wondering if the timing is off? The stuttering thing reminds me of my old truck that had a carburetor and if not adjusted properly would act like it wasn't getting fed enough.
If anyone knows what is causing this and the fix for it, I'd really appreciate the help getting my truck running solid again =)

I enjoy driving this truck a lot more than our CRV even though it's not really a looker. It'd be wonderful if this were something I could fix myself!

Anything y'all could provide me with would be massively helpful =) I'd love to get my average MPG from the 14 it's currently stuck on back up to the 17-20 range too! Anyone know if this is a possibility?

 

My thoughts is check to see if your injectors are clogged up or really dirty. Try running some Seafoam or comparable fuel system cleaner. I would start there and see if it still persists, then start checking other things such as fuel pump and the notorious splice.

Far as your lights go it could be a switch maybe, but really couldn't tell you as I have not had to deal with that can of worms (Knock on wood)

 

More questions now... sorry.
How would I go about checking the injectors?
Does this Seafoam stuff get put into the gas tank?
What is the "splice"?

Thanks for the advice/help!

 

Seafoam yes it mixes with your gas. If you really want a good cleaning for your system I would dump 2 cans for 22 gallons. But this stuff cleans pretty good so 1 can will probably do it.

Injectors you'd really just have to pull them out to be thorough.

The notorious splice is a poorly soldered connection below the relay box under the hood, check the FAQ's thread for more exact info on that.

 

For the light issue try replacing the switch on the column. For the engine problem repair the splice under the fuse/relay box under hood. It may look ok but for safe measures its best to just completely redo the splice so you know its been done and done right.

 

What about Marvel Mystery Oil to clean out the injectors?
How do i pull the objectors to look at them?
For the splice issue... could someone add a link to where this is posted so I don't brea/ruink anything trying to fix it =)

 

MArvel Mystery oil for oil system
(and no WD 40 either)
not for Injectors
If you know someone with a professional Injector flusher FORD cleaner is best value (at least for us)
If not use the Seafoam
cut the fuel filter open and see if it is full of crap when you change it
If crap in in-line filter pull the tank and clean and new in tank filter
(or do it anyway)

IS there a headlight relay if not install two (high beam and low beam)
check the fuze
So you do not have to replace the headlight switch twice!

 

I'm on my phone so I don't have time to read all of that long post, so sorry if I'm covering what you posted.

Since you posted what I quoted it sounds like possibly it is fuel related. Did you check your fuel pressure and volume when it acts up? That would be my first guess, which could be the sign of a bad fuel pump or clogged fuel filter or lines.

 

If you have a junked up fuel filter, your going to want to practically pull off the injectors and back to make sure its cleaned out. un-bolt all that and flush the fuel rails, and take an air compressor, your now disconnected fuel lines going from the fuel rail, try to put a little bit of gas in them, and blow the lines out with a compressor after you have disconnected them from the filter and from the fuel pump. Had to do it with mine when my fuel pump went, as when i fixed that i found the other gremlins hiding and killed them off while i was at it. Never run the same fuel filter for 19 years straight.... >.<

 

I have a new symptom I thought I'd share to help shed more light on what's going on with the truck. It's started idling pretty rough. The RPMs don't change but it's like it's having a tough time sitting there whether it's in Park, Drive or Neutral.

For getting the fuel lines, filter and injectors taken care of...
I'm inclined enough to do it myself as long as I have some directions to follow that will keep me from screwing it up more. I'm not what you would consider a gearhead, but am very mechanically inclined. Is there anywhere on these forums or in general you know of that could maybe walk me through it, or at the very least, provide a picture with labeled parts?

Thanks for all the help guys.

I'm going to get some of that Seafoam stuff today and run it through the tank and post an update later tonight/tomorrow depending on how long it takes for this stuff to work through it. I just filled tank with gas 2 days ago and have only put 30ish miles on it since.