2002 F-250 Power/ Mileage problem

[RDS in W PA]

Okay guys need to pick your brains. I have owned my 2002 F-250 since brand new. First year I owned it I took it to FLA. towing my fifth wheel trailer. Checked my mileage computer against actual fuel used for the entire trip. (Over 2200 miles) It was dead on, so I trust it to be accurate. I got 11.6 mi./gal. on my first trip down. The next year I went to FLA again. This time all the way down the best I could get was 10.3 mi./gal. On the way back I had a long uphill pull about half way home. During this pull I ran the truck in fifth gear, 55mi./hr, about 2750 rpm. This pull took about 8 minutes of steady hard running. Near the top of the hill my truck started making a different sound. Sounded like an aux. fan kicked on. That isn't really what happened but there was some sort of hum audible in the cab. From that point on the truck ran better. The throttle was more responsive and my fuel mileage improved back to 11.6 mi./gal. for the balance of the trip. This same thing has happened two times again since the first time. What is going on here? Is my catalytic converter plugging up and choking off my fuel economy and power? Could there be carbon deposits on my Turbo charger impeller on the exhaust side that I takes a hard run to heat up and burn off? Any one else have a similar experience?

[Patrick]

Does your truck have a cat? That sounds really weird, do you use a good injector cleaner? Have you changed your fuel filter lately? I dont know what the noise is, but I have seen bad fuel and fuel filters cause crazy millage results. Take your air inlet to the turbo off and look at the impeller wheel. Could be a couple differant things but I would start with the easy stuff.

[mschn99]

only think i can think of is maybe a fan clutch problem, that would explain the "roar".....

[bigcountrysg]

I don't believe your truck has a Catalytic COnverter. The Reason I say that is my 2002 F-250 did not have one on it from the factory. One thing I would recommend if you are unable to afford the nice 4 inch or 5 inch exhaust system is go to a local muffler shop and have them remove your muffler and put a straight pipe in place of it. I gained about 1 to 2 miles per gallon by doing that and it only cost 40 dollars at the shop I went to. I don't know the laws for the state you live in but right now in Michigan Diesel trucks are not regulated for emssions. Also I would invest in a good aftermarket intake system. That also helped me gain the 1-2 miles per gallon with highway driving. As for the loud roar I aggree with Marc and have to say it was your fan clutch. I would not guess that you have a problem with it but. Once inawhile my fan clutch will lock up and you can really hear that fan pulling air through the raditor. I also concurr with the other guys on the fuel filter/ fuel quality as well because I have noticed some brands of diesel fuel give me better fuel mileage then others.

[Patrick]

They did put a cat on a few years in the 90's. I know 94 for sure, a guy that works for me has one.

[Downunder]

That "roar" you mention, I experienced that today and I have heard it once before whilst pulling hard up a hill. Sounding like an auxiliary fan cutting in is how I would describe it also.

Marc and other more informed persons. is this a problem and should I get it checked or is the fan designed to "ramp up" when the vehicle is working hard?

Cheers,
Downunder

[mschn99]

Originally Posted by Downunder

That "roar" you mention, I experienced that today and I have heard it once before whilst pulling hard up a hill. Sounding like an auxiliary fan cutting in is how I would describe it also.

Marc and other more informed persons. is this a problem and should I get it checked or is the fan designed to "ramp up" when the vehicle is working hard?

Cheers,
Downunder

that is normal operation. When your pulling the hill you are making the maximum amount of heat the motor can...which then requires more air to be pulled through the radiator to cool it.....thats why the fan kicks in.......

[Downunder]

Marc thank you for the prompt reply. It is good to know that this is normal operation and not a problem.

Got my Donaldson severe duty air kit today and will fit it on the weekend. From all accounts it will allow the engine to breath easier yet keep the rubbish out, just what we need.

Again thanks for the information.

Downunder