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Old 10-08-2008, 05:26 AM   #1
Mobius118
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Member#: 159098
Join Date: Sep 2007
Chapter/Region: MWSOC
Location: Gurnee, IL / Madison, WI
Vehicle:
2005 LGT Ltd 5AT OBP
2003 WRX Stg4 PSM- RIP

Default Spark plug recommendations?

My bugeye has been suffering from some misfiring for a few months, and I'm thinking that the likely cause is the spark plugs, which have yet to be changed after 74,000 miles. Most of my buddies who tune and maintain cars have recommended NGK plugs. I was looking at the Iridium IX or G-power platinum. Does anybody have anything good or bad to say about these?

Also, equally important- should I be keeping the stock heat range or going one step colder. I know that the general rule is about ~75hp for one step colder. I'm at COBB Stg.2 minus an aftermarket uppipe with plans for VF-39 and STi TMIC later on. Is this enough to go one step colder or is it unecessary?

Thanks!
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Old 10-08-2008, 06:16 AM   #2
hotrod
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Join Date: Jan 2002
Location: 13.239@102.85 @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX

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Have you already read the spark plug FAQ listed at the top of this forum?

http://forums.nasioc.com/forums/show...postid=5927874

Larry
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Old 10-08-2008, 06:46 AM   #3
Mobius118
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Member#: 159098
Join Date: Sep 2007
Chapter/Region: MWSOC
Location: Gurnee, IL / Madison, WI
Vehicle:
2005 LGT Ltd 5AT OBP
2003 WRX Stg4 PSM- RIP

Default

Yup, I did read the FAQ but I just needed a little bit of extra information to make sure I'm making a good decision. No point in giving up money towards anything if you're not sure that it's right in the first place.
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Old 10-08-2008, 07:47 AM   #4
hotrod
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Join Date: Jan 2002
Location: 13.239@102.85 @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX

Default

Good, there are quite a few threads where this is discussed, but bottom line is that Platinum and Irridium plugs exist to improve emissions and have essentially no effect on performance. A working plug is a working plug as far as resolving issues like a chronic miss.

Spend $1.89 each for a set of garden variety plugs, gap them to 0.029 and see if they solve the problem. If not the problem is not the plugs. If yes and you don't want to replace plugs every 20,000 miles pick up some platinum or irridium plugs and put them in there. Their only significant advantage is they have very little electrode wear and can be left in for extended change intervals.

Heat range --- the plugs tell you what heat range you need. Read the cheap plugs you put in there for how far the heat discoloration band moves down the ground electrode. If they discolor more than 1/8 inch down the ground electrode you need to go a step colder.

http://www.empirenet.com/pkelley2/sparkplugreading.html

Larry
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