I have a new to me 2003 3500 4x4 auto with the 5.9 cummins that has 130000 miles. About 3/4 throttle when driving it has a hard spot. The hard spot is not there when the truck is not running. The only time i really notice it is pulling my camper cause its right at that point when u start up a grade and it needs a little more throttle. if u mash the pedal past the hard spot sometimes it will downshift and sometimes it will just keep pulling depending on grade and load. Transmission upshifts and downshifts fine. It 's not causing any problem just curious as to what it is.

 

As a guess valve body problem. The throttle valve is jamming at a certain spot because the valve is wore in the bore. As long as you shift points are ok its not an isssue but, it could become one any time.

 

If it were the valve sticking in the bore wouldn't it do it running or not, the cable is attached to the valve body when not running. A strange problem that i was hoping someone else had already diagnosed.

 

No, there is no pressure to set against the pistons when itss not running. The vlave bleeds line pressure to create TV pressure so there is a set of pistons and springss internally to control it.

Disconnect the TV cable and drive it to verify.