Hey guys! 2003 Evo 8, 135k. Engine is stock accept for exhaust.
Recently posted about having an issue running no boost. After investigating, found out my cat was plugged. So went catless downpipe.
Before having this problem, I had an issue where running WOT full boost, car would start to buck. Pulled my plugs, and cylinder 3 was fouled(may be related to cat being plugged). Since then I have had an issue with cylinder 3 fouling plugs. Here's a pic when I first pulled them, not sure how long these were on before I changed em

Before my cat was plugged and I was running full boost, it would foul every 3 weeks or so, but original plugs lasted months before the first incident. MTrying to figure out which route to go...what do you guys think?...I can't tell if it's oil, fuel or maybe electrical.

 

So wasn't sure how to start diagnosing the problem....thanks in advance! 👍🏽

 

I haven't noticed any smoke out the pipe on startup, or out the oil cap when I shut it off. But could it be a small enough break on the ring land enough to still foul the plug and and buck under load?

 

I would start with a compression test. Also you can try testing the impedance of the spark plug wire for #3 to see if its in need of replacement. It wouldnt be a coil because then you would have 2 fouled plugs.

 

Great, thanks for the suggestion! Got someone that's gonna do a leak down test also either this week or next pending bc of the holidays.

 

Deposits do look like oil, but it also look slike that plug isn't firing, at all lol.

 

yea, that one was pretty bad. These were in there for a while so must of accumulated over time.