Got a 97 with a 5.9 truck has 175,000 miles on it. In the winter I had the throttle plate cut and the timing adjusted made a big difference smoked a bit had to feather the pedal till the turbo and rpms caught up to fuel availability but lots of get up especially at the start of third gear. Since then though the power has really lacked and I have to stay off the pedal or it smokes (black) almost steady. I had an after market fuel booster pump installed along frame rail but no help in matter may even smoke worse now. Is the injector pump bypassing, or on its way out ,or the lift pump week or fuel heater not working?Seemed to happen right around the time bio diesel was introduced. any suggestions tips or diagnosis ideas welcomed fuel economy shot as well 75-100 fewer miles per tank.

 

Definitely not a week lift pump or injector, it's most likely quite the opposite. You're pushing too much fuel.

Black smoke = too much fuel or not enough air.

That also means your EGT's are probably through the roof. Do you have an EGT gauge?

Start with the easy stuff. Check the air filter, take a peek at the turbo vanes and make sure they are completely coated in soot.

Also, you injectors and valves are probably covered in soot by now. Get it down to about a 1/4 tank of fuel, dump 32 ozs of PS Diesel Kleen in with it and find a nice big hill. Load the truck up good (at least 4 - 6K) and run that hill hard a few times. You need to get the boost numbers up and the EGT's and cook some of hte carbon off.

 

what kind of boost numbers are you getting. . . .you might need to check your turbo for shaft play. . .no more than 0.020 linear, and no forward or backward movement.