Just bought this truck a few weeks ago, been busy and haven't had much time to work on it. It's a 2003 f150 super crew with a 5.4 & a/t. Had a bunch of problems, needed rockers and cab corners, power windows and locks didnt work, brake lights didnt work, needed brakes, speedo isnt accurate and ran real rough (but I got a hell of a deal!!)

Anyway, before I bought it I found about 10 vacuum leaks and figured that was the running issue. Did all the body work and fixed all the electrical (except speedo) and got a sticker on it. Well the vacuum leaks were not the only problem.

1) truck only gets about 6-8 mpg highway.
2) runs alright for first ~5 minutes then starts getting real rough. Wants to die after letting off the gas, rpm pulse at idle, but no hard miss.
3) no CEL or MIL
4) CHT reads ~318 at operating temp, temp gauge is normal.
5) fuel injector pulse width is about 11ms at idle (which I'm told is about 3x higher than it should be, but no info to back it up)
6) already replaced CHT, thermostat, bled coolant with no change
7) bought a $30 book of Haynes toilet paper, which I'm not even sure it'd work real well even for that.
8) also side note, if you unplug the MAF, truck runs way better, but still not road worthy. Also does not throw a code when you have MAF unplugged.
9) don't know when the plugs were changed, have new plugs but afraid to break one and need to do a engine tear down just because I wanted to change plugs and test compression, not until I have the extra cash at least.

This problem has me stumped. Which direction should I head? Is this a blown head gasket/cracked block? Bad water pump or clogged passage? Computer doesn't know if its coming or going? Any info/experiences would be greatly appreciated. Right now I have a $1200 lawn ornament (like i said, great deal) with a good sticker but can't afford the $30 a day in gas to get 20 miles to work and back. Not to mention I don't wanna cook the engine or clog the cats. I already have a j/y computer and water pump, just don't wanna throw parts at it after reading some forum horror stories.

 

Yes you did get a 'hell' deal.
It's not a deal after you get done with all the repairs.
Even if truck was given to you for free it's still not free.
You need to get a good scanner to look at the live data to see what's going on.
Three areas that will cause high fuel consumption. They are inoperative Ox sensors, stuck open thermostat, and cold signaling CHT circuit.
Intake air leak will cause stalling after warm up.
You likely have some combination of two or more issues by the description you gave on this truck.
It was abused and left go by the last owner.
Get a scanner on it so you know what's going on, to even begin to sort it out..
Good luck.

 

Thanks for informing me how deals and money work, I wasn't aware.

Anyway, I do have a scanner with live data. I'm new to the electrical side of automotive so I'm not 100% at what I'm looking at when I see the values.

I have replaced the thermostat and the CHT, not saying they aren't the issue, but i have replaced them.

ECT reads at 180 while driving. CHT reads in voltage, I believe around .77 when at operating temp (at work, I'll have to double check when I get home.)

Also noticed it will kick in and out of open/closed loop, is it supposed to open at idle and close after higher engine speeds?

Have not done anything with the O2 sensors other than verify they wires aren't chafed/broken visibly anywhere. What kind of values am I looking for to know that they are working?

 

First change to make is get the running temp up to 195 area.
Change the thermostat.
Good luck.