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Guest Message by DevFuse

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Spark Plug Observation

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4 replies to this topic

#1 Myxalplyx


    Old Wise and Dumb

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  • New Castle

Posted 16 February 2005 - 10:30 PM

Well, I drove around the neighborhood tonight so I could take my spark plugs out. 2 of them just 'clicked, clicked, clicked' when trying to take it out while the engine is cold (Don't do this. I wouldn't recommend it anyways).

Anyway, I took the spark plugs out and got a good look at them.

#1 spark plug was kind of dark but not sooty. Looked like it burned well but just a tad rich,

#2 spark plug was the same as #1,

#3 spark plug had some hard/greenish looking crap on the end of it. The tip of the spark plug wasn't perfectly angled/squared like the other ones. It had the figure like a burnt match of sorts. It was kind of rounded,

#4 spark plug was a perfect light brown color. It burnt clean and good.

#3 cylinder always have seemed to plague Subarus for various reasons (Sometimes #4). I have plans for more fuel. I never heard any detonation/pinging and the car ran great, even with the #3 spark plug looking crappy. My camera couldn't capture the detail so no pic.

Those of you that noticed similar/bad/strange things on your spark plug on #3 cylinder, what are your thoughts on this?

#2 tizzle


    Subaru Nut

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  • Bellingham

Posted 16 February 2005 - 10:50 PM

Isn't this why people do the parrallel fuel rail mod, because #3 tends to get the short end of the stick?

#3 4WDFrenzy


    Certified Subaru Nut

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Posted 17 February 2005 - 02:09 AM

Well my first thought would be antifreeze, like from a cracked head. But then after thinking about that for a sec, antifreeze usually leaves a whitish residue on the plugs. I'll see what my Chilton's Manual says and get back to you.

#4 subyrally


    Trust your Turbo-Lust

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  • frederick, md

Posted 17 February 2005 - 07:07 AM

try insulating the turbo from the engine a bit better, i know somee out here will say that the turbo isnt a problem, but when it rests over #3 and there are always issues with 3, then i tend to put 2 and 2 together. the extra heat from the turbo can and will adversly affect the cylender, ive seen it numerous times on wrx's, especially if its modded and been pushed for while. look into getting a turbo insulation kit, i think that you can get em for about $50 and they are made to take extream temps and help under hood temps and hp.

just my thoughts on the issue, that and the stock fuel system needs work.

#5 Do It Sidewayz

Do It Sidewayz

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  • Toronto, Ontario

Posted 17 February 2005 - 08:27 AM


Next time you are at the dyno, get them to throw the accessory knock sensor with headphones on the engine.....mainly on #3.

air/fuel ratios logged with a Wideband are great and all (hell i have a wideband at home for personal use now)....but knock is important also. You get all your power from timing. it takes longer to play with, especially on a car with a Distributor, but in the end you can tune for what fuel you have, and really get the most from the car. We were at the dyno about a month ago with my uncles 323 GTX, and we did not use the knock sensor...however the dyno operator told us if we were prepared to run race fuel, and spend time tuning the timing we could easily get 30 more HP.

#3 does get very hot compared to the rest, this is because of the turbo, fueling, and heat. There are ways of controlling each. However...9 times outta ten...when we blow up one of these things, it's #3. We blew up another one 2 weeks ago, and it was #3.....we've got alot of blocks with #3 blown...almost never the drivers side.

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