So been doing alot of research on spark plugs since I seem to be fouling plugs quickly (been running NGK 8's and now Denso IW24) but my guess is even though I have a high hp setup (500-600) I am on the highway 70-80mph for 80% of my driving during the week which is 500++ miles a WEEK. Could this be fouling out my plugs? Of course I get in boost quite often but I don't think it's enough to get the plugs "hot enough" to keep them from fouling out (misfiring mainly under load).

Plugs are more grey/black than a tan....Currently running 30psi but will eventually be at 40. Current plug is IW24 with maybe 1k-2k miles on it and is now misfiring (but only like 2-3 weeks for me) gapped at .023-.024 with feeler gauges. Currently blowing out black smoke like a diesel under boost and misses....If I throw in fresh plugs Im sure it will run like a raped again until I get some miles on them then foul out again. So does highway driving not like colder plugs?

I don't want to hear I shouldnt be driving a high hp evo as a daily driver

 

What's your cruising AFR's and fuel trims look like?

 

Average cruising afr's are around 14.5-14.9.....The fuel trims according to my scanner have always been under 10% if that helps...Was told by the previous owner it was a safe/richer tune

 

Any advice? Try hotter or colder plugs? Projected over non projected? different gap?

 

Ok so I learned that the back bolt closest to the block in the o2 housing is drilled into the exhaust part. That bolt had fallen out and had an exhaust leak there, after cleaning out all the carbon that built up in those threads and also installing a divided housing gasket so my dump tube isnt leaking at idle it now is so much quieter (obviously) and does not break up under boost.....as much...so thinking the exhaust leak was screwing with the o2 sensor and making it run funny? It still will break up under boost but only sometimes and much less of a cutout than before. It seems like the first couple pulls are always smooth and perfect but once it builds up some heat it starts to misfire on the pulls after that....Comments? Suggestions on whats going on here?

 

Any pre-O2 sensor exhaust leaks causes the sensor to read lean and thus the ECU compensates and adds fuel. However, your "black smoke like a diesel" during any WOT operation is all in your tune. The front o2 sensor is not used when you're in open loop.

 

Yeah I know what you mean but either way since I fixed the exhaust leak the black smoke has been reduced at least 65%, maybe it was the excess fuel from when it was still in closed loop, I dont know but it's running how it should know besides for some little misfiring after I do a couple pulls