hey guys i have recently purchased an evo 8. i was driving it daily for about 3 months before i had to do the head gasket and timing belt. ill tell the story from the beginning so maybe u guuys can see my problem. Obne day my buddy with his turbo civic wanted to race. so i went home quick to change my spark pluggs because i had a slight misfire and thought it would help. i switched them the ngk one step colder uridium pluggs. the car was running fine before i did this but the head gasket was going and it did need a better tune. once i changed the pluggs and turned the car on all it did was continuisly basfire so i shut her down. thats when i just decided to put her to the side and do the gasket and ****. So i took the head off and had it plained and all the stems and seals done. i got a thicker cosworth 1.5mm headgasket and i also did water pump and timing belt. the car was sitting for about a month while i did all that. Now when i start it it starts up but seems to be running rough. When it starts to warm up and drop idle i start getting a backfire. it feels like its almost running on 3 cylinders or sumtin. I did a compression test and they were all fine. i checked if it had spark and it does. i even changed the coilpacks to makesure its not my problem. now i do have crower 280 cams so idk if i just need to get it tuned or if sumtins still wrong.i pull the plug on cylinder 3 and it doesnt seem to make a change. idunno if its firing or not but it forsure has spark and compression. the pluggs are black when i pull them so im thinkin its getting fuel right? i put the old pluggs back in and it seems to run a lil smoother but i hear uridium pluggs are pregapped right so thats not an issue. I know thats alot but i really need help figuring this out. im new to evos so any advice would help.


the mods are:
fp green
crower 280 cams
full 3in turbo back
dejon intake
walboro255 fuel pump
act heavy duty clutch
arp head studs
electronic boost controller

all mods were on the car prior and were tuned on the car going by wat the previous owner is telling me

 

nvm got some help from a master tech from subaru ironically

 

Some cars don't take well to iridium plugs. Not sure if there's any rhyme or reason to it either. Some say iridiums make their car run much better, more power blah blah blah. I know plenty of evo guys who switched from $2 ngk coppers to $10+ iridiums and made their car run like poop even at idle. I'd try some fresh ngk coppers. With ur mod list you could go range 7 or 8. I'd try bpr7es, br7es, bpr8es, br8es. They are $2 a piece so pick one a see if it helps. I use br8es. They foul quick but work great. Keep the gap at about .020 - .024 area. It'll take some trial and error but its a good place to start.

 

what ended up being the issue?

 

yeah im going to try new pluggs. i was recommended the uridium ones but even after putting the old copper ones back in it idles smoother it felt. and the issue i guess is my timing is still off. i was told the black sut on my pluggs was from the exhaust because of the valves not opening at the right time. and the popping i am getting when it warms up and drops idle is the gasses from the exhaust passing through the intake valves. im going to to the timing again tomoro and hopefully that fixes my issue. Thanks for the input yoqsaahoth

 

my timing was off when I did mine first, I was having low idle/stalling, knock in high gears under boost, low oil pressure, etc.