Oil on lower spark plug only, not valve cover

[pcs]

staying up to date with oil changes i see. looks clean in there.

 

[MTF]

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.

What gap are you going with? Ford is using a pretty big gap OEM recommendation.
Try using a tighter gap.
And are you keeping up with injector cleaning? If the spray pattern is weak, it could the reason?
And running the highest octane available where you live?

 

[2011reptar]

What gap are you going with? Ford is using a pretty big gap OEM recommendation.
Try using a tighter gap.
And are you keeping up with injector cleaning? If the spray pattern is weak, it could the reason?
And running the highest octane available where you live?

I went with factory gapping. I replaced all 8 injectors as well just to be safe. All looked good, and the new ones obviously looked good as well before throwing them on. I am running 91 which is the highest here, though I have put octane booster in once to make 93 and it didn’t help with that, though I could hear a little less pinging when in low Rpm range on a gradient.

Something weird today is I left the truck running while fueling up - dumb but it was 3am and I was tired. But the truck started almost dying during the fuel up. Every few seconds the idle would dip and almost stall, then come back. Once I was done fueling it stopped… so maybe the other general idle issue is all fuel pressure related? I have fuse 27 relocated and the fuse itself looks fine.