Stumbling engine.

[1911 guy]

Ok my uncle has an 03 6.0 Bone stock with a bit over 100K on it. Has never had a programer on it. When starting it cranks good and fast but is a bit slow to fire up completely. You can tell a few cylinders are firing right off the bat but takes a few seconds before the rest start to fire off good. Idles good and smooth afterwards. While driving it accelerates fine until you get to cruising speeds then it randomly just starts to sputter a bit. not so much that it causes the truck to buck and shake but noticeable and audible somewhat. The sputtering will instantly go away with a bit of extra throttle input but will return later. some days it does it every 50 miles and others it will do it every 2 miles. Im not a PS guy so you may need to describe some things in a bit more detail on how we can trouble shoot this thing. Thanks for the input.

 

[Bad Moose]

May want to try pulling codes on it. Could be alot of things but kind of sound like a injector.