A little background. We bought my wife's early 04 2 years ago. It had 275k on it. Transmission (auto) had been rebuilt with all the goodies. Injectors redone. Air Dog fuel system. Bully Dog Triple Dog. We got it for $4k under nada book value. Got awesome fuel mileage. As in, I wont get into numbers because most of you will either question my mathematical ability, or drool over what it is getting now, after about a 10-15% decline.

Got a dead pedal a few times. Came back with the APPS code. After the tech at the shop she used to work at unplugged it, tested the voltage, and such, it worked well for a year. Then it got to the point of needing replaced. Got a Williams unit from Geno's. installed it. Did the recalibration procedure by the book. Got a code for the sensor calibration. Cleared it, and it never came back.

Over the course of the next few tanks, my wife mentioned a drop in mpg. Still not horrible for a 7000lb pickup, but not as good as before- down 2-3mpg. No gauges. Still runs like a scalded dog if you want it to. Transmission shifts as it did before. Doesnt matter where we get fuel, its about the same.

Any ideas?

 

What are the MPG's? Are you using the overhead or doing mpg by hand?

For maintenance, make sure fuel filter is good, and run some Optilube XPD or 2 Cycle Oil in the fuel for lubing the injectors. If you can get your hands on B20, go for it. If you run a cetane improver like Powerservice, run roughly 16oz in full tank for the next couple of fill ups.

MPG is very subjective, if you tires are low, if you are driving into a 30MPH wind, the temp outside is 20-40 degrees cooler etc.

Report back in, let us know whats up.

 

Does the 04 Truck have a catalytic Converter? I know some pre-600 engines outside of California had no cat.

I have no idea how long the cats in the 600-610 engines last, before clogging up. Anyone with intel on this, please chime in.