i was coming up interstate today and my truck started to run a little rough at an idle but once you throw a little fuel to it the noise stops! i just replaced radiator so i thought waterpump maybe now i have it tore down its not the water pump it sounds like its behind the timing cover any ideas on what this may be? i got to get this thing fixed its the only wheels ive got this far away from home

 

Fan hub?

 

not the fan hub because it blowed out 3 years ago ad i deleted it and went to twin electric fans

 

You can try cracking the injector lines one at a time.. This should help you isolate which injector/cylinder has a knock.

My engine started knocking real bad a few months back. If I cracked the #1 injector line at the head the knock qould go away 100%. I had that injector tested and it failed. I replaced the injector and all is well now.... How many miles on the truck???