ok i have a 2000 cummins it runns good and idles perfect:thumbup2: but when im crusing and just in the throttle just enough to maintain speed it raddles up a storm almost sounds like a little jackhammer:neutral: it goes away when i release the trottle it also goes away if i hammer down:woot: but then i get what sounds like a random pop comming through the stack:stuned: i have adjusted the valves and checked all that i can think of:banghead: does anyone have any suggestions as to what it could be

what rpm does it do this noise at? something is loose somewhere?

I think this has something to do with the delivery of fuel. Like air in the lines or a messed up injector.

extremely severe injector clatter perhaps?

It could be exhaust rattle from the exhaust gasses hitting the resonator.

the noise is at most all rpm above 1000 im thinking fuel but also am concerned that it could be something to do with my exhause due to the fact that i installed a 6in single stack back in the summer but i havent been able to find any info on that causing any probs however im still running the stock down pipe then it turnes to 5in under the cab the to 6in tru the bed. i also know the vp44 oump was replaced at about 120k before i bought the truck and it now has 160k it also had a low fuel psi light installed then which has saved my vp44 more than once in a year cause ive had 4 lift pumps fail it sucks settin on the side of the highway changin them

could check the injector line isolator hold downs. if they are loose they might rattle. can you recreate this by holding the throttle with your hand in the engine bay? take the cover off and hold it with your finger, listen around for the source.

ive tryed recreating the noise and finding it by having my gf hold the rpms at where it makes the noise and me under the hood and by ear or with a mechanics stetha scope i cant hear it ive searched the whole truch over for loose items i even adjusted the valves and looked over all the rocker arms valve springs and bolts under the valve cover i even ran 3 tanks of fuel with injector cleaner tru it and no help

reading your first post, im inclined to think this is only recreated under power. Also with a pop out of the exhaust could be to one injector being cracked and dumping excessive fuel? Almost might need a audio file so we can hear it. I know on mine, i hear the injector rattle when cruising, when i get on it it goes away and when i coast its gone. but nothing like you are saying with the jackhammer and popping...

ive talked to my dad whose been a diesel mechanic for close to 30 years and he said timming but idk im thinking injector too and really want to pull them and have them tested but this is me daily driver. and yess it does have a pop in the exhaust and the jackhammer sound was more described by my gf but that is pretty close to the sound. its worse than a valve rattle but nut as bad as a rod knock and the speed of it is faster with faster rpms edit: oh and the audio wont do much good cause with the stack it distorts badly due to the truck being so loud