OK so I bought my 03' evo 8 last summer, i drove it for about a month and it ran perfect, it only has 52,000 miles and the only mods are a 3" turbo back and a larger front mount(not sure of brand) I parked the car for about 5 months while i was overseas(im in the military) No one drove the car but i did have my mom go out and start the car every other week and let it run for about 10-15 mins so the fluids would get moved around. My problem is i come home and start the car up, seems to be running good, i take it for a spin and I notice it has a missfire under boost, its not immediate, usally dont kick in till about 4-5k RPMs, but it happens every time i get in the boost. So I did what i thought would be the quick fix, got new plugs. I pulled the old plugs out, they didnt seem like they were bad, just kinda old, i popped the new plugs in, same problem, missing under boost. So i go back and check and gap on the old plugs, they were about .030, I pulled the new plugs out(NGK iridiums) and check the gap, WAY off! the new plugs were at .040! so i set them to .030 put them back in, missing was less but still there, I did some searching online and read from a couple different places that the gap is supposed to be .027, so i pull em back out and regap AGAIN. I pop em back in and the miss seems almost gone, it doesnt happen every time i get in the boost now and when it does its just a real quick shudder, i figured it just needed a lil fine tuning with the gap or something so i shrug it off and continue to drive the car, BUT i wasnt driving around boosting every where, i drove it like granny, i just wanted to get to work and back that day so i was driving it easy. I drive fine all the way to work but on my way back home it starts missing BAD, feels like its only running on 2 cylinders! I limped it back home and i feel like im going to pull my hair out, this car has been trouble and ive only driven it a few times! I hope some one can help me out here cause i dont know what to do, the mitsu dealer hasnt been much help, they refused to give me the factory gap setting over the phone and said if i bring the car in to be looked at they are gonna charge me $90 a hour for labor! I unfortnatly dont have a mulimeter to check to coils, but i dont even know the resistence values anyways. Honostly i dont think this is a coil issue though based on how the car ran, i did do the idiot test and unplugged the coils one at a time to see if ran the same and of course it ran like poop so i know the coils are working at least a little bit. I have read a lot about the evo's having miss fire issues, so if someone could please point me in the right direction! thanks!

 

How much boost are you running? You should try gapping at .022 and see if that correct it.

 

how was the vehicle stored. Are you on the same gas you stored it with? could be bad now.

 

It didnt have much gas in it, i ran what was in it out and filled it back up with 93 octane. It was stored outside with a car cover on it. Its running stock boost, im trying to find the part number for the plugs i got but cant seem to find the box i bought them in. I think i just may need new plugs cause these new ones i got from advanced auto parts were a little different from the ones i pulled out, the thread was longer and the porcelien shorter, they may be the wrong ones, they thread in just fine though. Whats a stock number for plugs that are proven to work good for a car with my mods? just a 3' turbo back and larger intercooler, stock boost

 

bump for a spark plug stock number!

 

okay so i did some searching and found a lot of people use the NGK IGR7A-G. is this a good plug? do i have to gap it? what is the stock gap so i can check it?

 

I think it might be more of a gas issue, especially since there's no fuel filter, are you getting the misfire code?? or can you just tell it's misfireing?? I DD mine and I was getting the code alot, changed the plugs and it didn't really help much, then I added some fuel system cleaner and haven't really had a problem, I would try that

 

if you do that put your old plugs back in till you run that fuel through your system and then change them.

 

i already ran the old gas out, i did get a missfire code. i cleared it once and it came back of course. i bought some fuel injecter cleaner today. ill dump that in and see if it helps i guess, i still think i need new plugs especially after i gapped those iridium plugs cause i probibly messed em up when i did that, really all i need now is a good plug to get and what it should be gapped at so i can check it

 

i meant run the gas out once you add the fuel injector cleaner. then throw your new plugs in. I guess it doesnt matter but it stains them and might make it harder to read them later on.

 

oh ok, well i just pulled the plugs that are in there now and they look like they have been in there for a few months and its been like 2 weeks, kinda blackish, also some oil on the coil stems, so a new valve cover gasket will be going in too. I think the game plan will be to order new plugs, im gonna get the NGK IGR7A-G unless someone tells me otherwise, ima change the valve cover gasket and toss the new plugs in and hope that does it

 

ngk brp8es. autozone or advance auto parts should have them. they are way cheaper than iridium because they are copper. most tuners suggest these. make sure that you gap them at .028.

 

ok, i really dont know much about spark plugs, and this is biggest problem cause it seems everyone has a different opinion about what plugs are best, remember my evo is pretty much stock and running stock boost. Now im reading that NGK BPR7ES's are best, and if gapped at .024 will be fine. anyone think this is fine or no? the gap seems low, but i really have no idea, PLEASE help! i am completly lost with this spark plug thing, i need to know which ones and what to gap them at!

 

so im guessing the difference between the BPR7ES's and the BPR8ES's is the heat range? i live in ohio so i need a plug that will work good in cold and warm weather. I have no idea on what heat range changes, only that a lot of people change them when they crank up the boost, i have no plans to crank the boost past 20 psi, i have a EBC but its just to play with the gain and get the boost to settle at 20 and hold there as long as possbile. and the gap thing, ive heard of people gapping everywhere from .023-.030 which one is right for stock?

 

its prob not your plugs. Its likely your wires are shot or your coils died.

Wires die after about 40K or so and coils vary. My coils died at 63K.