Apologies if some of the diagnosis on this seems a bit sketchy, I inherited this job this evening as some one thought the 6 o'clock news means it is time to go home.
This motor arrived with us this morning suffering from a rough idle and a harsh vibration under load at engine speeds below 3,000 rpm. one of my technicians was working on it and scanned for fault codes, he retrieved 1 code: p0674 glow plug cyl 4 open/short circuit. leak off test results were normal, injector current was uniform on all 6 injectors fuel pressure low and high seem good (I don't have exact figures) a relative compression test passed OK. Injection quantity specified & actual match up to within 1 mg. we replaced fuel supply with fresh fuel to no avail. this thing goes like a train once above 3k with no issues but below that, it has power but it would shake the fillings out of your teeth. I expected to find misfire codes on this but none no matter how hard you flog it. Has anyone ever come across this before?
Thanks
Mark
Just to add when cold this runs fine for a minute or two so we have ruled out a mechanical issue (I think)