You might want to check the breather tube and make sure it's not plugged or kinked.
The common rails have had problems with injectors, could be an injector causing it.
You said the oil looks OK. Does it feel thin...like diesel is mixing with it? Is the oil level overfull?
2000QC,SLT,SB,4x4,Intense Blue,Auto,4.10,DSS,AFE Megacannon PRO GUARD-7,silencer ring MIA,Edge Comp-pump wire untapped,Rip's 4in Fair Shake Exhaust,Isspro EVs fuel,boost,pyro,FASS 95/150, S/S '03 trackbar bracket, Thuren '03 trackbar, HTS Ultimate Duty trans w/ billet input & output, 89% Suncoast convertor, 150HP MAXsticks
'06 Liberty CRD, Inferno Red Crystal Pearlcoat, GDE ECO tune
'12 Dodge Grand Caravan SXT, Bright Silver Metallic
'98 Jeep Grand Cherokee Laredo