Oil on lower spark plug only, not valve cover

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2011reptar

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2011, 115k. Have had a slightly rough idle issue for a while. Among other things, changed all 16 plugs and 2000 miles later decided to pull them again to check gapping. When I originally pulled them, cyl 5 and 6 bottom plugs had oil on them on the end going into the combustion chamber. Anyway, all gaps were correct but I noticed the same two plugs had oil on them again. I confirmed this is NOT a valve cover leak, the outside of the plug hole is dry. Any ideas on what may be causing this and if it effects much? I understand the top plugs do most of the work and the bottoms basically just help with emissions? Anyway, not sure how to resolve this issue if someone knows what can be done, I hope it doesn’t require pulling heads.
 
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pcs

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any pics of the plugs? what other maintenance items have you performed? if you have no engine lights to point you in a direction, you can address the idle issue with easy maintenance items. clean the throttle body, MAF, and possibly use a top end cleaner. when you changed the plugs did you inspect the coil boots? 2 decade old truck going to need some tlc. all engines will burn some amount of oil. it can come from blow by past the rings, pcv stuck open, worn valve guides or valve seals, etc.
 

Mad Zeus

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I didn’t have the rough idle . About half my lowers had a little build up the rest looked new . If your loosing oil I’d be concerned if not drive faster it’ll burn it off . Did you replace the coils & wires ?
 
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2011reptar

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any pics of the plugs? what other maintenance items have you performed? if you have no engine lights to point you in a direction, you can address the idle issue with easy maintenance items. clean the throttle body, MAF, and possibly use a top end cleaner. when you changed the plugs did you inspect the coil boots? 2 decade old truck going to need some tlc. all engines will burn some amount of oil. it can come from blow by past the rings, pcv stuck open, worn valve guides or valve seals, etc.
No pics, but the end was wet enough to bead up, almost dripping but not quite. It’s for sure oil, not gas which is concerning after such little mileage. Cylinder 5 and 6 only. I fired the parts cannon when I bought it about 3500 miles ago chasing the idle issue, and just to freshen up a 14 year old truck I knew nothing about - 8 coils, 8 injectors, 8 wires, 16 plugs, PCV, TB, O2 sensors, purge canister, MAF sensor, air filter, all OEM. Cleaned inside of air intake, did a seafoam treatment through crank case and through vacuum system, did an engine cleaner in oil before changing, reset KAM and did a relearn procedure in FORSCAN, did a compression test, scoped the cylinders and even popped both valve covers to look at the springs... All looks fine, just a little oil in cyl 5/6. No CEL, no performance or mileage issues, and no changes from before swapping out the old parts, just a slightly rough idle and sometimes almost dies when shifting into park, will dip to 200rpm and then back up only when stopping and shifting into park.

Right now I’m more concerned with the oil situation than the idle as I understand the Raptor variant of the 6.2 has a more aggressive overlap than the one in the f250, so a little choppy idle is normal and I may be chasing ghosts there. I just want to get ahead of an issue before I get stranded somewhere considering the amount of oil I’m seeing on the plugs. I should add the top plugs were all spotless. According the maintenance records they were changed about 10,000 miles ago… they looked newer. Most of the other bottoms looked fine as well. Of all parts changed, 2 coils had bad resistors, but otherwise sorta think I wasted my money replacing things.

I guess it would have to be guides/seals or getting past rings as you said. I wonder how long this can be lived with before it gets much worse or ends up causing other issues.
 
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pcs

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stock raptor cams shouldn’t have any “chop” bc they have to pass emissions. also, plugs shouldn't be spotless after some use. they should be turning light brown. if it really bothers you, maybe a compression/leak down test can address any concerns with engine health. i had a similar issue with the engine wanting to stall randomly at idle and what fixed my issue was a new fuel pump. your truck over 2 decades old its going to have some quirks.
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