Casey - Yes the truck does run better when you take your foot off the gas but anything past 1/2 thorttle it starts to hesitate / breakdown. I double checked the exhaust and no issues there. The truck actually has no catalytic converters on it and is dumped under the cab with a glass pack. I drove it around last night to see if speed made a difference and there was some but not sure what to make of it..as long as i kept it under 1/2 throttle it ran fine, however once I get into overdrive around 60mph+ it runs as if there is a "mis" somewhere.

I got a fuel pressure guage and will check that tonight and a friend is giving me a new set of wires...heck i may spend 20 bucks and put new plugs in to see if maybe there is a simple issue there i need to go back and check.

 

Also, forgot to mention that the truck has not had converters since I have owned it for 10 years so I am not contributing any fault to the sensors and such there. As for the smog equipment / thermactor stuff this was removed a few years ago when I realized it was all dry rotted so not concerned there either.

Damn truck drove like a dream 3 months ago as it was my daily driver 24/7 until the problems now so just got to keep plugging away at it. Even if replacing something doesnt necessarrily fix it, it only makes it better later on since I will never sell it!

 

just my 2 cents but I just went through the EXACT same problem with a 2004 F150 5.4....I know this forum is for earlier trucks but I chased my tail and it was a CLOGGED CAT.....I also know that you have no cats but I wonder if the exhaust could somehow be clogged....neighbor's cat crawled in there maybe.....something....everything you describe matches my symptoms and I changed EVERYTHING before I discovered the clogged cat thanks to this forum....

 

Come to think of it I havent seen the grey cat that used to tear into my trashcans!

Appreciate the feedback and a second look surely cant hurt! Definetely appreciated!

 

when I took mine to the local muffler shop he took it inside and came back out a few minutes later and said to me...."take it for a test drive and see how it acts"...when I got to the truck I could hear an exhaust leak....pft pft pft so I drove it and it had much more power with no shaking....bogging...etc that I had before under load over 30 or 40 mph or so and when I got back I asked, "did you pull the o2 sensor out?" (read that here as a test) and he said "no, I drilled a small hole in the pipe just past the headers....those cats are notorious for the 2004 - 2007 ford trucks, I've changed 400 or so this year for the dealer" 200 bucks later truck runs great since it has all those new parts on it!! I have the old cat and the ceramic is busted into pieces clogging the outlet...the whole problem was caused by my fuel rail not seated properly (after I had it off to fix a vacuum line on the back) and was misfiring on that side, dumping gas into the cat, gas gets hot and explodes blowing out the ceramic.

I think they have flow meters that you can try to measure how much back pressure and flow you have to diagnose clogs...good luck, hope you find the problem....

 

WOW damn good information thanks man!

 

yep...no problem....lol on the grey cat dude!! maybe you can lure him out with some tuna....lol

 

Sure sounds to me like an exhaust restriction somewhere. Is the truck running lean? I had a bad hesitation due to a faulty egr valve sensor as well. I would take a plug out of each bank and see how they are burning.

 

Checked the fule pressure last night and everything was right in line wit the specs in Haynes Manual:

Engine Off - 32 PSI
Engine Running (Vaccuum line plugged) - 35 PSI
Engine Running (Vaccuum line unplugged) - Pressure jumped to 41 PSI which the Haynes book says anywhere between 5-10 PSI is good.

Also, unbolted all of the exhaust up to the collectors on the headers and it was clean pipe throughout. Decided to powerbrake it in the garage with the lights off to look for any arching or missing from the wires and didnt see anything. (truck doesnt seem to act up until over 3K RPM and I didn't get it that high because I prefer not to drive through the garage wall!!!)

CaseyLandscapes I am going to do that as well! Bought new plugs today and will be checking them as I pull each one. Truck doesnt seem to run lean anymore, few months back it did when the Idle Air Bypass was faulty but since that was fixed its been okay.

I also borrowed my Dads Volt/OHM meter and will be testing the throttle position sensor since its the oldest of the replaced parts.

 

Well, mine's fixed. I decided to go ahead and replace the cap & rotor and the plug/coil wires with a new set, and found the spark plug boot on #7 plug wire had a pin hole in it and was arcing to the cylinder head under load. It'd been like that for awhile because the boot was heat-hardened from the arcing and it cracked open when I pulled it off.
Drove it 85 miles today up and down hills and such and she ran just great. You might want to check your plug/coil wires again. All it takes is a tiny hole or crack, and it might only arc under load like mine was doing. Good luck...

 

Hey Guys,

THE TRUCK IS FIXED!!!!

Heres what the deal was:

I was stil convinced it was a fuel issue so I rigged up the fuel pressure gauge to the rail as the book calls for, however I ran it through the vent window and set it on the dash so I could see it as I drove dwn the road. Sitting at the stop sign I was dead on 42PSI...Pushed to Half Throttle..she dropped to 24PSI...smashed the gas and Down to 17PSI...

So I had a buddy of mine, Old Ford Mechanic for 20+ years come by and run some electrical test...entire truck came out perfect but 2 things: Sending Unit in the Tank was bad AND the electrical connector (the oval shaped one for the pump) was faulty on the tank..not the wires running from the truck. After replacing the pump this weekend, and all of the fuel filters the truck runs like a Singer Sewing Machine!!!

I also decided to bite the bullet and replace the pump on the rail and returned the old one at no cost...so all in all 2 new pumps and all new filter. On a side note for anyone pulling the fuel pump off the rail the sicket size for that bolt is 8MM.

Thanks to everyone for their suggestions and all the help. Good luck with your future builds and I pray that the time I spend on this site, for at least a few months, is for advice and not something else broken lol!!!

 

That's great news, congrats! Mine is still running good too. Here's to getting these troublesome problems fixed!