Kracka

iTrader: (49)

It is seemingly far too common for the spark plugs in the X to fail in one way or another. Please vote in the poll and feel free to post your experiences. If you've had multiple failures you can select more than one option.

I replaced my original plugs at 25k miles with them in good shape. I bought replacements from the Mitsu dealership (NGK's in Mitsu packaging), one of which then failed after 11k miles (insulator dropped over the electrode). No engine damage occurred and NGK replacement (non-Mitsu packing) plugs were then installed.

3dman1

My plug failed in #4 and my motor failed at the same time. The insulator came loose and fell over the electrode at full throttle. Im not sure if that is what damaged the motor or if motor damage caused the plug to fail. There was no obvious damage to any internals but the piston cracked at that time. There was no damage to the head or valves or piston tops but the sleeve was out of round due to excessive pressure. Not sure if the plug caused the damage or if the damage caused the plug to fail but im really leary of the stock plugs.

murlo26

iTrader: (9)

I'd say the plug was screwed because of too high cylinder pressure and the heat generated with it.

People with 800whp still run stock plugs without issue.

That being said I too have seen plenty of spark plug problems, but they seem very random, as in some are built motors some are stock motors and varying level of mods.

I have always run stock spark plugs, but that being said I am on my 4th or 5th pair at like 32k miles, so not a great sampling lol. I replace them with big mods and motors

Anarchy99

iTrader: (196)

Its my opinion that the jackhammer like cylinder pressures of detonation is what cracks and breaks the porcelain and folds over the electrodes.

Kracka

iTrader: (49)

That's a probable explanation for some failures, but not all based on what I've seen.

justin81

iTrader: (14)

Mine failed. #2 and #4 at the same time. Ceramic insulator over the electrode causing piston #4 to melt.

My plan is check them before and after every event, check them at every oil change, and change them every 10k miles even if they don't show signs of wear.

It becomes the chicken or the egg story. Did my plugs fail causing engine issues, or engine issues cause the plugs to fail. Either way check your plugs often.

I've also heard of new cars fresh off the truck having ceramic over the electrode during test drives. So............ who knows.

AWDTerror

iTrader: (2)

Wouldn't the insulator falling cause a rich condition in that cylinder?

Inprogress

iTrader: (30)

I replaced my plugs when I bought my car (with 35k miles on it), the plugs on the car weren't in good shape at all...I was told by the shop that the plugs made it seem as though the car had been sitting/not driven for a while.

Is it still suggested to go with the OEM plugs? I'm thinking I want to replace them, just for peace of mind now that I'm nearing the 10k mark on my ownership of the car.

black95tt

iTrader: (13)

Did you torque the plug properly? Seems weird that your first set was fine and the second failed shortly after. I remember reading a post where someone said that NGK attributed a failure such as that from being over torqued.

Kracka

iTrader: (49)

I've been installing spark plugs in turbo Mitsu engines for over a decade. Evo X plugs are failing widely across the board and it is not uncommon at all, and as the poll above shows factory installed are failing too. The issue here, in my opinion, is quality control on NGK's part. A local here had a set fail right out of the Mitsu box, and another set fail within 2 days (both sets were professionally installed). This is not a good sign for spark plugs that are designed to have a maintenance interval of 60k miles.

black95tt

iTrader: (13)

Gotcha. Wasn't trying to imply you didn't know what you were doing. It very well could be a problem on NGK's part.

Inprogress

iTrader: (30)

I thought spark plugs were just hand tightened, I didn't know a certain amount of tq was in the equation?

black95tt

iTrader: (13)

Yes, they definitely need torqued.

http://www.ngksparkplugs.com/techinf...stallation.asp

joeyhauser

iTrader: (4)

The insulator broke on one my factory plugs. I think it was around 15k miles

3dman1

The problem with this statement is none of the plugs with broken porcelin show other signs of detonation. The strap and plug gap is perfectly normal,color and overall condition is normal as well. nkg says its from being over torqued but that seems off to me when they fail after thousands of miles on the same tunes ect.