Misfiring from cylinder 5,6, and 8.

[Gustavo]

 

 

 

I have one stumping me. I have a 2004 early build 6.0 that misfires on cylinders 5,6,8 only at idle when warm in drive. Trucks has good acceleration and drives great. DTC P0278 sets. Noticed when coming to a stop the whole bank cylinders 2,4,6,8 drop and as soon as I stop at idle in drive 5,6, and 8 begin to drop -10 rpm . Relative compression test passes, manual compression all cylinders are about 380psi. Ficm m power remains at 48 volts. Fuel pressure is at 67 psi. I replaced the fuel check valves and fuel filter standpipe ( fuel filter standpipe was broken). No fuel aeration.  When I disconnect the icp sensor the engine smooths out the power balance is straight. I replaced the icp sensor and connector., concern was still there. Fuel filters where changed and lof was performed.. I replaced all 8 fuel injectors  with the early style correct fuel injectors. But the misfires remained at 5,6,8. I air pressure tested the high pressure oil system with the engine hot and hear no air leaks. I switched the high pressure oil rails to the opposite sides and retested. Replaced the driver side high pressure hose, both high pressure oil standpipes, and both check valves on the high pressure oil rails. Installed a known good ipr and concern still present. Power balance remained at 5,6, and 8. Noticed when pressing on the brake pedal hard the concern goes away. Removed serpentine belt and concern went away. Inspected pulleys but all pulleys were good. Fan does not stay engaged. Noticed it does this based on IPR load. Decided to get the engine hot and removed the driver side valve cover. Ran the engine with driver side valve cover off and noticed excessive oil was misting from the top of all 4 injectors on the driver side at about 800 rpm and above. Don’t know if this is normal but any help would be greatly appreciated. I have contacted hotline gave them my diagnosis but they basically told me to replace the high pressure oil pump and contact them only after I replaced it. I replaced it doubting them and the concern was still present. After I told them results and the concern  remained they basically said I was on my own and to escalate it to the and service manager. I’m the only diesel tech at my dealership. And the Shop foreman has no diesel experience.