Horrible fuel mileage w 07 Pete 379, NXS 625hp Cat

I've noticed fuel firing in the #### turbo after that little arm to the EGR in my truck was stuck all the way open. That was causing it to spit an sputter slowing down cming off of off ramp's and such plus loosing power and getting ###### fuel milage. Had the EGR replaced and it still kept doing the same thing. Never could figure out what the problem was causing it. It was an 07 Century without all the new emissions BS on it. I also noticed it worsened with the use of ULSD.

 

You could order a 625hp Cat as a factory option.

 

I wouldn't think so. Everytime I've had that code it ran great up until the fault. 99% of the time shutting it off and restarting cleared the code, and restored power. I think I've had that sensor has been replaced I believe 3 times in 250k miles but hasn't been touched in the last 100k, must have got a good one this time.

 

Cat told me having oil over full can cause this code

 

If its the sensor it probably won't derate,but if if your losing oil pressure to the VVA under the valve cover it will derate.At least thats been my experience.

 

Did they check the boost wasn't leaking out through the air compressor, have seen that a few times.
Lower exhaust backpressure and fuel restriction helps but an ECM tune seems to have the best results.

 

I still think that you may need a set of injectors. If the fuel rate was low when they had it on the dyno and had to adjust, how much did they have to bring it up? Adjusting fuel flow conpensates for injector wear. You pulled heavy with the engine and it is a 625, there has been alot of fuel pumped through those injectors. Cat used to say anything over 100 000 gallons was time for replacment. Does this engine have injector warranty still?