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ITS TURBO TIME!
05 LGT limited
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2,778 Posts
Discussion Starter · #1 ·
Ok Guys I just finished up my other thread about the misfiring and determinied i had a melted spark plug. So like i said i put new plugs in a week ago and everything was fine. Well last night im leaving a car meet in the area and dont you know the car starts misfiring again! so i get it home and park it for the night. I got up early this morning and pulled out the #4 spark plug from the cylinder and sure enough the gap is completely gone again. Only this time it doesnt look like it melted. It actually looks like something is hitting it. small scrapes are visible and all. Which leads me to believe that a piston is traveling WAY too far during a stroke or something like that. So i put a new plug in this morning and instead or tightening it way down i backed it out by about 2-3 threads. Any gurus please chime in and let me know whats going on!
 

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needs more cowbell
95L, 07 2.5i, R6
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9,316 Posts
wrong plugs?

Ok Guys I just finished up my other thread about the misfiring and determinied i had a melted spark plug. So like i said i put new plugs in a week ago and everything was fine. Well last night im leaving a car meet in the area and dont you know the car starts misfiring again! so i get it home and park it for the night. I got up early this morning and pulled out the #4 spark plug from the cylinder and sure enough the gap is completely gone again. Only this time it doesnt look like it melted. It actually looks like something is hitting it. small scrapes are visible and all. Which leads me to believe that a piston is traveling WAY too far during a stroke or something like that. So i put a new plug in this morning and instead or tightening it way down i backed it out by about 2-3 threads. Any gurus please chime in and let me know whats going on!
 

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02' PSM WRX
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1,535 Posts
seems like the plugs are wrong (too long) or maybe at one point someone damaged the area were the plug threads into and now when its tight it goes in to far... (IMO)
 

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ITS TURBO TIME!
05 LGT limited
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2,778 Posts
Discussion Starter · #4 ·
These are the same NGK's ive been running for years! Never had a problem with them till now. And like i said its only #4 cylinder. So i backed it out a few threads and we'll see how that goes i guess.
 

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needs more cowbell
95L, 07 2.5i, R6
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9,316 Posts
Compare the plug lengths and model numbers to eachother... they could have given you one wrong plug in the batch.
 

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ITS TURBO TIME!
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2,778 Posts
Discussion Starter · #8 ·
ok so the pics are gonna take a while because i dont have a camera that will zoom in far enough to see the gap on the plugs....but ill try something else! As far as the plug lengths being different i dont think it has anything to do with that because like i said the plugs had been in the car for almost a year with no problems and then suddenly i had a problem with the #4 cylinder spark plug.
 

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'06 LGT
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8,334 Posts
Why not just replace them, they are cheap enough and easy to do....


This would solve any of the problems you might incur in the future.
 

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ITS TURBO TIME!
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Joined
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2,778 Posts
Discussion Starter · #11 ·
Plugs were already replaced last week. So far no problems. I am just trying to figure out why this could have happened. And there wasnt any oil in there but when i pulled the plugs out i noticed A LOT of carbon build up. And also just yesterday i pulled out the Idle Speed sensor in the throttle body and noticed a ton of carbon built up on the sensor....enough that it was making my car run like crap. So i cleaned that off with cleaner and put it back in. Seafoamed the hell out of the throttle body and intake put it back together and she ran like a champ.
 

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needs more cowbell
95L, 07 2.5i, R6
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Maybe a big enough chunk of carbon broke loose and dented the plug. Or something further upstream could have fallen into the cylinder???
 

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ITS TURBO TIME!
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2,778 Posts
Discussion Starter · #13 ·
Maybe a big enough chunk of carbon broke loose and dented the plug. Or something further upstream could have fallen into the cylinder???
^ Thats what im thinking. Because like i said the second time it happened the spark plug was actually dented and not just bent. And im guessing the carbon build up on the IAC was from the PCV valve recirculating carbon material from the crankcase back into the intake. If im wrong about that i would love some of these subaru gurus to chime in!
 
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