07 5.4L Fuel Issue
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Junior Member
Joined: Feb 2016
Posts: 4
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07 5.4L Fuel Issue
Since I bought this truck in August, it's had a funny issue... at 30-40 it's like it has a spot where it has no power, you hit 50, and it picks back up fine.
I was told the cats were bad, so I cut them out, welded in straight pipes. Same issue.
Had a miss, ran rough at idle so on... replaced plugs, coils so on, MAF.
Still.... same original issue.
Found crack in exhaust manifold, changed that....
Still same issue.
I don't have o2's where my cats were, I was considering welding in a nut to screw them into. The front 2 o2 sensors that were before the cat are still there.
I don't think that's the issue since it was happening before I removed that stuff.
I'm getting a fuel smell in the cab I'm not sure when that started, I thought it would stop after having exhaust welded up properly.
I've read here on the forums that if I didn't torque the plugs to 25lbs they do that..... (I just held the part of the ratchet where you change the direction and snugged them down that way.... last triton I put plugs in, I blew the threads out the next day that was a 99 though).
Would a loose plug cause a loss in fuel pressure?
I took it to a shop, they couldn't find the issue but they said it had low running pressure. I'm going to test the FPDM tomorrow... or at least take a gander at it.
When I back up and turn or something like that it dies (sounds like fuel pump to me but they checked it and said it was fine)
I'm running out of ideas.... please help
I was told the cats were bad, so I cut them out, welded in straight pipes. Same issue.
Had a miss, ran rough at idle so on... replaced plugs, coils so on, MAF.
Still.... same original issue.
Found crack in exhaust manifold, changed that....
Still same issue.
I don't have o2's where my cats were, I was considering welding in a nut to screw them into. The front 2 o2 sensors that were before the cat are still there.
I don't think that's the issue since it was happening before I removed that stuff.
I'm getting a fuel smell in the cab I'm not sure when that started, I thought it would stop after having exhaust welded up properly.
I've read here on the forums that if I didn't torque the plugs to 25lbs they do that..... (I just held the part of the ratchet where you change the direction and snugged them down that way.... last triton I put plugs in, I blew the threads out the next day that was a 99 though).
Would a loose plug cause a loss in fuel pressure?
I took it to a shop, they couldn't find the issue but they said it had low running pressure. I'm going to test the FPDM tomorrow... or at least take a gander at it.
When I back up and turn or something like that it dies (sounds like fuel pump to me but they checked it and said it was fine)
I'm running out of ideas.... please help
Thread Starter
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Junior Member
Joined: Feb 2016
Posts: 4
Likes: 0
I went back to the mechanic that found the fuel pressure issue. He said he tested the pump, the FPDM and all that jazz, he suggested it could be something to do with the tune since the motor came from a king ranch, I've heard though, that in that case a 5.4 is a 5.4, the different computer tunes it the way it needs to be.
I've never messed with the computer, and most mechanics don't want to flash it because I don't have cats or o2s in the back, says it'll put it permanently in default mode until that is repaired.
Should I just replace it anyway? I'm at a loss
I've never messed with the computer, and most mechanics don't want to flash it because I don't have cats or o2s in the back, says it'll put it permanently in default mode until that is repaired.
Should I just replace it anyway? I'm at a loss