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Old 02-04-2005, 12:05 AM   #1
sajohnson
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Member#: 6140
Join Date: Apr 2001
Chapter/Region: MAIC
Location: Middletown, MD, USA
Vehicle:
2002 WRX 5MT Sedan
WR Blue. Cobb Stage 2

Default Spark Plug Condition

I just removed the spark plugs from my 2002 WRX. They have 75k miles on them (I know I should have replaced them sooner).

They all look about the same and don't seem bad considering the mileage. My question is, why does one side of each plug have a dry brown powdery residue while the other side appears to have gotten most of the wear?
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Old 02-09-2005, 04:01 PM   #2
Z28Hokie
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Here's a good link, pictures aren't "great" but they're ok:

http://www.theultralightplace.com/sparkplugs.htm

When you say brown powdery residue I'm assuming you're referring to the coloration of the top example- which is ok. It shouldn't be excessive- just like an area thats "tan".
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Old 02-09-2005, 08:58 PM   #3
sajohnson
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2002 WRX 5MT Sedan
WR Blue. Cobb Stage 2

Default

Thanks for the link.

I should have been more clear -- the dry brown powdery residue seems normal, it's the fact that it is only on one side of the plug that I found strange.

The other side of the ground electrode has the obvious wear and black coloration. All four plugs are like this.

I took a couple pictures but could not figure out how to post them. If someone could tell me how to do it I'll post a picture.

This is most likely normal for this engine (since all four are the same) I am just curious as to why the deposits one the plugs are not uniform.
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Old 02-09-2005, 09:46 PM   #4
Hayes
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The slight difference in discoloration is due to the way the gas charge hits the spark plug. Normal on every car I've owned including my 2.5L subaru. eddie
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Old 02-10-2005, 10:56 AM   #5
Z28Hokie
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Quote:
Originally Posted by sajohnson
Thanks for the link.

I should have been more clear -- the dry brown powdery residue seems normal, it's the fact that it is only on one side of the plug that I found strange.

The other side of the ground electrode has the obvious wear and black coloration. All four plugs are like this.

I took a couple pictures but could not figure out how to post them. If someone could tell me how to do it I'll post a picture.

This is most likely normal for this engine (since all four are the same) I am just curious as to why the deposits one the plugs are not uniform.

Oh, it's because of the way the flame propagates in the cylinder, temperature variations, fuel concentrations, etc. Anyway- nothing to worry about- they'll always be a little more tan on a different side. If you index your plugs- you'll see the "side" is always the same. I forget if the tan portion appears on the side facing the exhaust or intake valves...I know it's one or the other.
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