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Discussion Starter · #1 · (Edited)
[SOLVED] LIMP MODE, 04 6.0 limp-mode, derate mode, de-fueling... please help

Long time reader, new member because im really at a loss. I got a 2004 F350 6.0 that's going into limp mode, or derate mode, or de-fueling whatever its called. when the truck reaches operating temp it wont rev past 2500 rpm, has plenty of power, and I can still drive on the highway, if I shut it down and restart its fine for several seconds, does it again. it never fails, if I drive easy the whole time or if I beat that crap out of it once it warms up it goes limp (that's what she said). ive heard multiple opinions on what would cause this. the truck is completely stock with the egr unplugged (it was doing it before I unplugged the egr), and no check engine light and no codes stored according to my scangauge 2. here is what ive done/checked so far.

fresh oil/filter
replaced both fuel filters (autozone, was doing it before filter change)
Checked FICM voltage, doesnt drop below 47.5v
Checked FICM sync, in sync (1)
checked oil pressure, 590psi at idle, almost 4000psi at WOT
checked boost, 0-3psi at idle, just over 20psi at WOT
checked fuel pressure, 56-58psi continuously
checked ECT and EOT, when it went limp EOT was at 158 degrees, ECT was
at 166 degrees, but both stayed reasonably close together
checked MAP sensor, idle 15.1, high idle was the same, WOT went up to 21 before I had to let off the throttle
checked EBP sensor, idle 17.1, high idle 18.9, WOT went up to 32 before
I had to let off the throttle
I really don't know what the MAP and EBP readings mean

I don't really know what else I should be looking at, and help would be really appreciated.

SOLVED: BAD EBP SENSOR - truck thought it was boosting 40psi
 

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Discussion Starter · #4 ·
Are you running a Motorcraft oil filter and an OEM cap?

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no its a bosch filter, but it was doing it before the oil change, and my high oil pressure is good
 

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Snake your pretty knowledgeable I know there is a high temp limit that will put you in defuel but is there a low side limit?

I mean he seems to be running awfully cold eot and ect unless he is in a -35 deg. ambient.

Just wondering.
 

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Discussion Starter · #6 ·
Snake your pretty knowledgeable I know there is a high temp limit that will put you in defuel but is there a low side limit?

I mean he seems to be running awfully cold eot and ect unless he is in a -35 deg. ambient.

Just wondering.
actually im in S. Florida so yah, 80 degrees outside, and those readings are what i took when it first starts to happen, im sure i can get it hotter, although i do drive around and it doesnt stop unless i cycle the key
 

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Gotta go to the doctor for a few hrs but I am gonna think on this a bit.
 

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Discussion Starter · #9 ·
does anyone know if trans temp will make it go into limp mode
 

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no its a bosch filter, but it was doing it before the oil change, and my high oil pressure is good
The easiest and least expensive way of starting your troubleshooting would be to begin here. I'm not sure this is what's causing your issue, but a friend had similar problems. It got to the point where he couldn't start his truck at all, even when cold. He installed an OEM cap and a Motorcraft filter and the truck has never run better. Might be something to consider.



Snake your pretty knowledgeable I know there is a high temp limit that will put you in defuel but is there a low side limit?

I mean he seems to be running awfully cold eot and ect unless he is in a -35 deg. ambient.

Just wondering.
Thanks, but I'm definitely on the dull side of bright. :hehe: There isn't a minimum EOT/ECT where the truck will defuel.



does anyone know if trans temp will make it go into limp mode
It will not

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Discussion Starter · #12 ·
The easiest and least expensive way of starting your troubleshooting would be to begin here. I'm not sure this is what's causing your issue, but a friend had similar problems. It got to the point where he couldn't start his truck at all, even when cold. He installed an OEM cap and a Motorcraft filter and the truck has never run better. Might be something to consider.

thanks. the reason i went with AutoZone filters is because when i was trouble shooting the problem i wanted to rule out the filter. I knew those filters are crap and OEM filters are recommended but i figured brand new should at least let me rule out filters. I did figure out parts at International are half the price then at ford so i got the blue spring kit ($37), and ill be getting new filters from them. There labor rate is also half the price, so i think by next week if i cant figure it out. I just wanted to figure it out myself cause thats the only way to learn
 

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Discussion Starter · #14 ·
Totally understand. For whatever reason (size/design of the filter and what cap it might work with) the 6.0 hates aftermarket oil and fuel filters and their caps.

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Yah I keep hearing that. It does have OEM caps though
 

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2005 F250 FX4 Lariat CCSB - EGR deleted, IPR coolant filter, figuring out what else.
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MKEEVO or Snake did yall ever find the problem? I am currently experiencing the same problem.
Check the original post again. It appears to have been edited with details of a resolution.
 
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