I have a miss as far as I can determine it is #6 cyl. I have eliminated the injection pump (VP44) because I can open all the fuel lines(short of #2,because of the intake) that make a difference in the RPM's (other words 2 cyls missing)except for #6 which has fuel being delivered,thus I have eliminated the VP44,I guess I need too make sure the valve's are opening correctly(which I thought I already did,but need double check)I have had the Injectors cleaned and set for proper pop pressure here at Diesel Specialties,No codes, so I know that I need to pull the head(not what I want to do) unless someone has another suggestion.

Compression check?Like JL Welding a while back had a similar miss and it turned out to be something in the cylinder either a cracked piston or a failed rings. I'm not say this is your problem but it worth looking into checking the cylinder health after 850K miles.

Was afraid you would bring up cracked/broken ring,I was thinking of buying a inexpensive compression gauge and adapter since I will probley only use it once or twice.

Well there is only 2 things it could be...* Misfiring injector* Poor Compression not capable of firing fuelHow about valve lash? :shrug:But since the injectors have been bench tested it only leave the other... :think:Anyone else have any other ideas?

My old motor would set a idle all day and sound just fine, drive it 300 yards down the road and it would start a slite miss. It had to do with heat as soon as the Egt's went up that would open up a crack in block,pistons or rings. New head did nothing.I do have a well stocked parts supply though.