Freightliner M2 with Cummins ISC 8.3 uneven idle, won't rev.

[Rawze]

(08-07-2025 )wrench buster Wrote:  Hello, I ran a system pressure test today and it didn't hold within specs. I found inj # 1 was leaking bad when I turned the engine off. I thought alright I found the problem, however that would have been too easy. I replaced # 1 with a Cummins re-man and the rail pressure held within specs. I ran a injector return test under hi pressure and it was within specs. (80 ML) in 1 minute. I am really stumped on this one because it still idles rough and misfires upon acceleration. The HP pump produces 29,000 psi so I don't believe that's the problem. I am leaning towards defective injectors or an ECM issue. If someone can help me narrow this down I would very much appreciate your help. I have no codes, if it was an electrical issue I believe it would throw a code.It feels liike ALL cylinders are misfiring upon acceleration not just 1. When I do the cylinder cut out it seems like very little RPM loss on ea. cyl.

Regards Wrench Buster

Is this engine de-mandated (deleted)?.. If so then the program needs to be copied out and sent to me for a review of what someone did in there. - For all anyone knows, it could be throwing 50 faults and some idiot suppressed them all, making it not show anything wrong.

Also.. you might want to do this .. to ensure its not something external causing it to run like crap...
ref: https://rawze.com/forums/showthread.php?...6#pid80656

... it will also run like crap if the crank or cam position sensors are not reading correctly.. and/or if the overhead cam has slipped,.. or if the tone ring on the crankshaft is loose.