will not accelerate when rolling

check for a pto switch that is turned on even if truck dont have pto there are wires behind the dash for one
also if you roll fast enough will the cruse speed up the truck or just nothing

 

is your speedo reading right a loose yoke nut or bad vss might cause a derate will it rev up at all or act like no tps responce
do you have computer there you can check on the tps sencor there is a off idle switch if its not showing thats its moving it wont let it rev can be bad wire to ecm

 

When trying to accelerate under load are you getting black sooty smoke out the pipes?

 

Had this problem on my 2003 C-15 ... Sometimes it would idle but you step on fuel and it would just idle. Sometimes it would start behaving this way with no warning. The cure: my truck uses regular metal spin on fuel filters. I must use one that has a separate rubber o-ring for the filter that is mounted on the frame. If I use a filter with a built in o-ring it may or may not function properly. Even though I have a Cat, I have had mechanics tell me my frame mouned filter mount is for a cummins. I use a fleetguard FS 1000 and never have a problem.

 

And I mean the rubber o-ring that is maybe 1.5" in diameter that you slide up the pipe that u thread your filter onto.