12.7 detroit studders and knocks

I would say fuel knock from bad injectors did you do a cut out test or just change them and how does it run under load and what inj height did u set go by valve cover or just what you were told

 

Sounds like fuel knock can be caused by warn rings how many miles does truck have and if it was me I would like to have a cut out test done when its cold just to see if I can get it down to one cylinder but getting a bad injector out of the box is a lot more common then you would think
Does unit have any codes or check engine lights

 

Does the engine go into high idle when started cold? If not, it's possible the ECM tempature sensor may be bad and causing wrong injector timing when cold. I fought something simular for a while on a 12.7. Come too find out the engine thought the water temp was 75 all the time and this threw everything off.

 

Get it to Detroit and let them keep it overnight and dyno it in the cool morning. They should be able to tell you if it's electrical or mechanical. That's cheaper than throwing dollars at it. I put in new injectors only to have mine do the same thing. Lesson learned.

 

Hi been having same problem with my 60 series 12.7 mine is a 97 get a injector cut out test but do it at idle an 1000 rpm if the test shows different injectors between the tests you have air getting in fuel.You can also take the return line off put it in a bucket with fuel start the truck if u have bubbles next take the fuel line off going from the filter to the pump put it in a bucket of fuel start the truck if the bubbles stop the air is between the filters an the lines from the tanks if u still have bubbles its probably an injector not seating hope this helps