Hello, We recently added a 2002 Kenworth T800 twin screw day cab tractor to our fleet. Truck has 605,000 mi on the chassis, approximately 300,000 mi on the engine. Engine is a Detroit 60 series 12.7, stock everything paired to a Eaton 10 speed and brownie box. Truck runs great, and exceptionally clean no smoke whatsoever during normal operation. The truck has an intermittent issue where after coasting or very light throttle input on a down hill it will cough or starts sputtering if you will and blow some grey smoke as the RPMs pick up when the accelerator pedal is pressed. The smoke smells of raw diesel. Once RPMs pick up it clears up. We have completed the following repairs to ensure that it is not a mechanical failure prior to chasing an electrical or software issue. The air filter, both fuel filters, fuel feed lines and crossover valve have been replaced, and we replaced the APPS sensor and wiring harness as a precaution. A scan of the truck does not yield any trouble codes. Prior to our purchase the ECM was flashed with the factory tuning from a dealer which was a "Low NOX" emissions friendly tune. After extensive trouble shooting and time online we have settled on this emissions friendly tune being the culprit as it is regarding the timing too far in the ECM's low demand parameters and the injection timing while it falls in those parameters is causing the cylinders to be over fueled and it is too rich when power is demanded. The truck did not have this issue when I purchased in Phoenix AZ, but the issue showed up immediately as I approached 4000 ft elevation. I took the rig to a shop, they came to the same conclusion I did and claimed they could tune the truck, however after having the truck a few days they said they could not tune it, as they did not have the original Detroit tuning files. I have a guy who can connect to the truck and allow remote access to the truck, but he does not have any tuning Do any of you know anyone who has a tune or the ability to tune this rig so we can get it on the road
Because it is in a PacCar chassis, PacCar will basically do nothing. If you would like it back to original, take it to a Freightliner dealer. Yes you read that correctly-Freightliner dealer. Most diagnostic/tuning equipment that's independent won't correct issue. Freightliner will reprogram according to engine serial number through Daimler. If you want it turned up it can only be done with accordance of Freightliner and most likely 500 hp @ 1575 torque will be max. * A real tune-up, only consists of adjusting valves, injectors and jakes. What people are referring to as a {tune-tune-up} is trying to do a bypass to more horsepower. A real horsepower/torque change is called a rerate by manufactures/dealers.