Spark plugs have Sludge/Rust!


2004 RX8
Alright so yesterday I was driving and smashed a bit in 2nd gear and my CEL started blinking, car bogged down. Pulled code and it was cylinder 1 misfire. So today I changed the plugs since I recently bought the car and it just rolled 65k, figured might as well do them. While I was changing the plugs, from left to right (cylinder 1-4 I believe), cylinder one's plug had a sort sludge/carbon all around where the coil attaches. Cylinders 2 and 3 had rust/corrosion around it, pretty much where it meets the engine after being fully screwed in. Cylinder 4 was clean for most part.

My question is, what would this sludge/carbon/rust be from? As for mods on the car it has Cobb SRI, turboxs BOV, a cat removed from exhaust, no tune or AP. Here are some pics,
Spark plugs.jpeg
Water is getting down your plug boot past the valve cover. Use dielectric grease on the boot lip to keep water out.
Thanks for the reply. So you think that's cause of sludge as well? Any suggestions about how to clean the crud out?
Agree with above. And those NGK plugs are the correct part number, but are gapped way too large, by my eyeball estimates. They need to be no more than .030". It is hard to get a consistent, hot, reliable spark when the gap is too large. If you have replaced them, be sure you use stock heat range if you are running stock boost level, be sure they are irridium tipped, and are gapped correctly. The water got in there from some idiot using a water hose under the hood. Don't do that.

I agree to use dielectric grease on the boot tip. I do not recommend dielectric or anti-seize on plug threads. Leave them bare. Coatings interfere with heat transfer from the plug to the cylinder head. Its not just about electrical conduction. The ability of the plug to retain or transfer heat is what heat range is about. To little transfer and the plug runs hot and can cause detonation and rapid tip erosion. Too much transfer (colder heat range), pulls too much heat away to the cylinder head and the plug will foul and misfire.
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Thanks for reply. Yeah I just got the car about a month ago so musty have been previous owner? Or maybe from a car wash?

The ones I bought were gapped at about .030. How do you recommend me getting the crap out from cylinder? Just blow it out?
Is it actually inside the cylinder head, on top of the piston, or just inside the valve cover around the outside of the plug? If the latter, try using vacuum hose attachment to a shop vac to pull it out.