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Discussion Starter · #1 ·
I am pretty much out of ideas what is the issue with my truck. But here it is.
2004 F-350 6.0L late build - no
Back story

Started to get coolant pukage and had over 16psi pressure. Tore down the engine and found the PO used black onyx gaskets. Already had studs. Had heads machined and put everything back together. Truck ran great before the build. This is where the fun begins. No STC fitting.


Trucks starts up no problem hot or cold. Runs great when the truck is cold. Has tons of power. Once the EOT gets above 120F it falls flat on its face. It runs really rough, lopes and misses and shakes the whole truck. It has absolutely no power. It will not rev. above 1500RPM in drive but will rev. no problem in neutral or park. In drive the truck will barely move. Has no boost either. Truck does not smoke at all. A slight smell of unburnt diesel but that's all. At first I was getting contribution / balance codes. No the same code back to back other than #5 and no more than 2 at a time. Replaced #5 injector but still randomly getting #5. I could start truck, pull codes, reset, turn off, start the truck again and have a different code each time. Totally random. I loaded up my SCT Extreme street tune and truck acts the exact same way expect I do not get any codes.

TLDR - truck runs great cold, but horrible when warm. Seems to be temperature related.

Attempted solutions and PIDS.

Double checked push rods and rocker arms. All good.
Replaced #5 injector. Code still randomly comes up.
Replaced IPR valve - connector on IPR broke during build
Replaced ICP and pigtail. ICP builds under WOT correctly.
IPR stays around 24%
HPOP replaced last November.
New stand pipes and dummy plugs. No STC fitting.
All new orings and copper washers on injectors.
Polished spool valves with 1000grit wet sand paper.
Replaced FICM harness. Connector to #5 was damaged and could of shorted out.
Fresh oil change T-6
Fuel pressure stays at 60psi under all conditions.
Cleaned EBP and MAP.
FICM voltage stays between 47-48 under all conditions.
battery(s) test out good.
Alternator puts out 14
Passed bubble test
Passed buzz test cold/hot

I think that covers everything. Might of missed something.


Fixing Broken Stuff
2,078 Posts
Polished spool valves with 1000grit wet sand paper

I've tried buffing the spool valves before and it didn't work out, after buffing them I didn't have any stiction and I tested it with a Hickok G2 (you tube it) but it had misfires issues, the fix was new Motorcraft injectors.
So using the 1000 grit makes me wonder if you have some injector issues.
Your ICP % at 24% make me think you have a HPO leak. Is that 24% hot?
I didn't notice anything with your PID's that stood out to me. I'll look at it again tomorrow.
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