DP Lost power.

[expedition1]

I have a 2005 Expedition that has a CAT C-7. Recently I have experienced a loss of power , nothing extreme , but the coach will not pull hills as it used to. I have replaced both fuel filters and it has made no difference.
The air filter has been replaced recently. I always get my fuel locally at the same location , could it be bad fuel ? It starts , idles , and runs on the flat perfectly with no smoke or hestitations.

Where else could I look ? Has anyone ever had any luck using an additive ?

Thanks in advance.

[D Lindy]

Have you ever had the upper rack assembly (valve train) adjusted? depending on your mileage this might need to be done and could be the source.

[dnystrom]

What is the turbo boost reading when under load like going uphill?

[twinboat]

You want to look over, all of the 3" , or so, tubes and hoses, that come from the turbo charger, thru the charge air cooler (CAC), to the intake manifold.

Any air leaks will cause a loss of boost and result in a loss of power.

The harder the engine works, the more boost it builds, so hill climbing would be where the problem would show up.

[expedition1]

I am the original owner and never had the valves or anything else done on the engine , only regular maintience -oil changes , filters , etc. Also I do not have a gauge that shows boost so I am in the dark on that one.