2004 F150 5.4 high calculated load, low power

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Mar 31, 2010
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Location
Iowa
Hey guys, kinda stumped on this one... My personal truck thankfully.. This issue has persisted since I bought the truck a couple of years ago - basically it's a turd compared to any other 3V 5.4 I've ever driven. I've gone through a whole lot, but the only thing that sticks out are high long term fuel trim and high calculated load.

The back story - a clean truck that I bought off a customer who didn't want to pay to fix it's issues. Had a pile of miles (204k) but was in good shape other than needing some TLC and the usual 3V timing work. So I used all OE parts, a new HV/HP oil pump and went up a grade to 5w30. Also had Trav service the injectors and replaced the fuel filter. Right from the start, it was always a pooch and sounded labored under light acceleration. Timing was correct. Never really looked much into it as the engine always had a noise (turns out it had a spun main AND a spun rod bearing, but hey, it lasted almost 10k miles lol)... I rebuilt a different 3V with all the same, but new goodies that I used on the first. The only difference is that I installed a set of Gibson SS headers. Hoping that the problem had corrected itself with the new engine I took to the road only to find out it hadn't. This time I wanted to investigate - everything I can find looks normal. I have a set of reference values that Ford published for this truck/engine and all that I have looked at are normal accept for the calculated load. They list values at idle, 30 and 55 mph (15-17%, 16-25% and 30-50%) Mine are 20% at idle and 80%+ moving! Trims at idle are close, but rise instantly once I'm underway. Interestingly STFT is basically right, but LTFT will be at least 15% to as much as 30% under load - seems to be more connected to RPM than load as I towed a van back from out of town a while ago and watched trims closely. Even at highway speeds with a trailer and van in tow, trims were 15-20%. But I can see 30 by flooring it down the road while unloaded.

Things that I have done/checked

Rebuilt short block, heads checked
New OE Ford timing chains/guides/tensioners/phasers - and yes, the timing is correct
New O2 sensors with the engine
Verified good MAF
New OE plugs/coil boots
Fuel filter
Another set of freshly cleaned injectors from Trav (thinking maybe the others were gunked up because of seeing constant addition of fuel to the trims)
Checked fuel pressure on the scan tool AND manually via an adapter/gauge - pressure was maintained at spec even under load while trims climbed
Checked exhaust for restriction with backpressure gauge - none
No codes
Probably more things that I have forgotten about

If I can figure out the cause of the artificially high load, I'm sure trims will come down to normal

Any thoughts? Anyone come across this before?
 
Is it getting up to operating temp? Does it have the correct ECM? Could a bad knock sensor keep the timing retarded? Is the torque converter engaging and disengaging correctly? What is the rear end gear ratio?
 
So a correction is in order... The values I reported were taken with a handheld Launch CReader 4 and they may be quote wrong!

I plugged my Snap On Solus Edge in and the idle readings are normal, the 30mph is 30 and the 55mph is a little over 50
 
Is it getting up to operating temp? Does it have the correct ECM? Could a bad knock sensor keep the timing retarded? Is the torque converter engaging and disengaging correctly? What is the rear end gear ratio?
Yes, up to temp (new OE stat)

No clue on the ECM - was going to have a chat with Ford on ECM/flash

The timing values I see align with the reference chart

The trans/converter does seem to operate normally, though I did have one converter in a hot rodded car fail and give me similar issues.

Gearing was 3.55, but I regeared to 3.73 with no change
 
I know it doesn't completely matter, but somewhere along the line, the trans was rebuilt
 
Have you smoke tested the intake system and also checked the EGR? No codes is weird but I would pinch off the evap, brake booster and other vacuum lines just to see how it reacts.
 
I haven't smoked the intake. There is no EGR on this truck - I can and probably will check the vacuum lines, but trims are good at idle and idle quality is actually pretty good, so I'm not expecting to find much there.
 
I was going to say the CAT but it looks like you checked that
That was my guess too.

The other thought is that "tuners" often know how to fix the inherent defects in the factory ECU tune. Mine did not give full throttle until 4500RPM and redlined at 5000. UGH. The tune was a godsend for my 2009 F150 4x4 Lariat.
 
This is a longshot, but cheap and easy to test - hook up a vacuum gauge and check vacuum at idle. I haven't used one in a few years, but IIRC you want to see a steady 18 - 21" at idle.

You'll find all sorts of tests on line to diagnose late timing, restricted exhaust, etc.
 
That was my guess too.

The other thought is that "tuners" often know how to fix the inherent defects in the factory ECU tune. Mine did not give full throttle until 4500RPM and redlined at 5000. UGH. The tune was a godsend for my 2009 F150 4x4 Lariat.
Something you can do is......... remove the Oxygen Sensor before the CAT to see if the vehicle runs better .
 
What’s your full throttle calc load and your MAF values?

Alot of these 5.4Ls are complete dogs to start with. We have an 08 F350 with a 5.4 for a service truck with a reading body on it and it’s a turd. Your foot has to be near buried all the time to get any kind of reasonable acceleration out of it.
 
Where did you check for exhaust pressures?

Wondering if a cat is broken internally and reducing flow.
 
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