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Q: Starts fine, engine gets warm it starts to lose power & the engine wants to die. on 2004 Ford F-350 Super Duty

Fuel filters, oil & filter changed 500 miles ago, purchased fuel and put in diesel fuel conditioner 70 miles ago. The fuel conditioner is "Power Service" Diesel Fuel Conditioner, and the 15 gals. of fuel was bio diesel from Shell. About 5 miles ago the truck started fine but after driving it for 4 or 5 miles it began to lose power. Long story short what I found was the truck would start fine when it was cold but after it warmed up it began to lose power until it died. Yesterday I removed, cleaned and reinstalled the EGR valve but it still runs the same. Any ideas?
Thank You,
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Great advice from Bob. To suppliment:

Ford trucks do NOT like Bio-Diesel. Ford's position is that the percentage of acceptable Biodiesel fuel is limited to 5% (until the current model year and the 6.7L Power Stroke, that is...)

Basically, it's scientifically proven that Biodiesel fuel literally creates a chemical reaction that causes delamination of the fuel tank found in your truck, and all other Ford metal tanks. This delamination causes metallic particles to become ingested into the fuel system, clogging the fuel filter, but also damaging many components on the way to the injectors. If this has happened, you will notice metallic debris in the fuel filter.

A revised fuel tank is available from Ford to reduce the delamination issue. They do not, however, cover this repair underneath any kind of warranty. The repair is very costly, figuring cleaning, replacement of appropriate contaminated parts (even the electric pump may be necessary), and replacing the tank and sending unit.

To note - I do not in any way know if this is what you are experiencing. Your symptoms are definitely consistent with what i've seen in the field. One tank of Biodiesel will not cause the problem by itself, necessarily, either. It's a cumulative issue. I have done a ton of research on this subject and understand a great deal about it.

Now...with the 6.0L, there are other possible problems, such as high pressure oil system issues, low pressure to high pressure branch tube oil pressure leaks, fuel injector control module issues, turbocharger coking issues from unburned fuel, EGR system issues - including the valve which you cleaned (if it was coked up badly, you may have more to clean to restore power...), etc etc etc.

A specialist fluent in the 6.0L is really a valuable resource local to you. I wish you luck!
Drain some fuel from the fuel filter to see if there's water or any dark-colored goo in the fuel. If so, replace the fuel filter. You may have gotten some contaminated fuel. This cold happen if there's water in the fuel, or 'asphaltines' which like like black tarry goo in the filter. I've gotten ashpaltines, totally clogged my filter and could have totalled my Diesel fuel injection system if I hadn't found it. I just by chance checked my filter and found it just in time. It's from the Diesel refiner, and can accumulate in the fuel truck. I wouldn't think that the fact that you bought a Biodiesel blend at Shell is a factor. If it's contamination, it could happen anywhere in the chain. Contamination can come from the refiner or the distributor or the fuel truck or the gas station tanks in the ground. Asphaltines are a result of imperfect refining and should not appear but do from time to time.
If you can not cure the truck with a new filter, take it to a Ford specialist or a diesel specialist.
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