What could have caused oil to leak into the 8th spark plug hole? It’s causing a misfire on cylinder 8 drivers side and I’m Really confused.

Honoredebalzac

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Hi everyone. I’ll try to keep this short.

checked with OBDII scanner and said misfire in 8. Pulled it and the one next to it and 8 was really oiled up; 918378F9-4D08-46F8-AF8F-8E54B303EB80.jpeg
I am really confused by this. As you can see the entire plug was wet, but I’m pretty sure the bottom got wet from what was on the top as I pulled the plug out, because when I first went to change the plug I pulled my socket out before I pulled the plug and it was oily, so I think it seeped from the top down. If it was due to a piston ring or something the top wouldn’t be oiled right?

At first I thought maybe the valve cover seals but it would leak up right? It wouldn’t make sense to me. Obviously I need to find out what did this before replacing the plugs and such. Any ideas or similar experiences?
 
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Jaskim06

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My valve cover was leaking. Not the best design the way they used the studs for valve cover with idk what you call it o ring washers? Not sure correct term but mine is a washer with gasket material around it. It's very thin. It needs to be more like a thick o ring. So if you try to tighten too much they just leak like a siv or break in lil cracking pieces. That was my issue. I put a lil high temp rtv around them new, let set up then put them in. No leaks for a few years now. Here's what the new ones look like.
 

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Ballyhoo

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Can't say I've ever seen one that oil coated on the insulator side. I'm in agreement with Jaskim. If the porcelain were only speckled tan I'd say valve seals, known for these heads.
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Honoredebalzac

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Sweet thanks everyone. I changed out the plugs and swapped the 8th coil pack just cause and it’s running without the misfire. I also took a closer look and it does seem to be the valve cover gasket I can see some oil building up after I took it for a spin and popped the hood.
I’m gonna change out the valve cover gasket tomorrow and hopefully she’ll be ready to roll again.
 

Jaskim06

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Sweet thanks everyone. I changed out the plugs and swapped the 8th coil pack just cause and it’s running without the misfire. I also took a closer look and it does seem to be the valve cover gasket I can see some oil building up after I took it for a spin and popped the hood.
I’m gonna change out the valve cover gasket tomorrow and hopefully she’ll be ready to roll again.
Just really look at the bolts and seals cause mine looked good until I tightened them down and saw tiny cracks around them. Then cue the oil leaks!! Like I said it's a bad design. The kind on a 350 chevy is much better. As long as you snugged them bolts down no leaks. Idk how many times I've had a customer say I've got leaks and the cause was too much torque on the valve cover bolts. I just tighten them down with a 3/8 rachet with the head not the handle. Just snug. I'm sure there's a torque spec but with non critical clearance parts like this I use hand torque spec. Lol some ppl go way over board. Like a foot and a half screw driver through the oil filter to get it off over board!! Too much. Glad you found the problem! Another thing is cheap gaskets. I love to save money like most but some stuff you can't go cheap on. Seems like ford products always gave me best results with gaskets and filters etc. A few bucks more is better than a few less and more work and doing job over!!
 
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