spark plug fouling

[RenegadeT]

I'm going to spinoff a parallel thread to my head-gasket-swap-after-p0301-code thread, and talk about the oil system and maybe engine knock/pinging I had.
Quick summary; new to me 2018 JL 3.8L in 2021 with under 10kmiles on the odometer. After a few months of ownership, still getting familiar with this new Jeep, I remember noticing some pinging under load when hot. Forum searches showed this is 'normal' for these engines...great, ugh. Also smelled oil/sulfur cats after spirited red light launces and on ramp merging. I ran a few tanks of 89 octane with no real change. Fuel economy seemed to drop off at some point too.
Regular oil changes every 6-8kmiles, started noticing the level getting low. Never seen any external leaks or smoke out the tailpipe.

Then there's the coolant system. Again, I had read that the JL engine fan was extremely loud, and I experienced that on 4wheeling trips, crawling all day. I didnt pay attention to the on board coolant temps, but never had a coolant warning light popup or noticed the gauge in the Hot position.

So now I had the CEL for misfire Cylinder 1, experienced rough idle at startup, and had coolant disappearing with no external leaks. I am in the process of taking the heads off to replace head gaskets. I took the passenger side spark plugs out a few weeks ago, did not like the oil on rear cylinder. Yesterday I finally looked at the drivers side and they are worse.

Any thoughts on these plugs and the story they tell? I plan to replace PCV valve during reassembly. Maybe I'll know more when i get the heads off.

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[RenegadeT]

 

[RenegadeT]

I just noticed I marked the rear passenger side cylinder like a V8, hmm lol.

 

[RenegadeT]

So when i pulled the heads off, I wasn't terribly surprised to find lots of carbon on the pistons tops. I soaked with WD40 scrubbed with a green scotch brite pad. #1 where the misfire code and head gasket leak occurred cleaned.up real well; been steam cleaned with coolant for a bit.
The drivers side seemed worse..
EGR cooler right there maybe sending more heat to the head. No exhaust manifolds on these engines, just a cast collector in the cylinder heads? Seems crazy to me.

I showed the pics to the guy that machined my heads. He just said something generic like "sh!t gas nowadays, they all look like that." . Not quite what I expected, maybe this is normal.

I still find it hard to believe a good clean running engine will leave this much carbon in the cylinder. Thinking about running higher octane gas and decreased oil change intervals. Also have a new PCV valve to install, will compare the old/new part numbers i have and look for online discussion.

 

[Wabujitsu]

I’m thinking that running top tier gas would be just as much, if not more important.

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