I own a 2004 Pontiac sunfire the two spark plugs closest to the passenger side have a light brown powder on them the other two spark plugs are perfect what does this powder mean. Is it normal?

This doesn't sound like a tuning question.





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Were you driving behind a confectionery truck?


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Usually a light brown or tan color on the white insulator indicates proper temperature - not too rich or lean. http://www.sparkplugs.com/sparkplug411.asp?kw=Normal+Plug+Wear&mfid=0

Most haynes manuals will tell you how to read your plugs properly. If the other two look fine or not tan/brown they may actually be runnign a little cooler than the other two which is ok - possibly smaller gap or just a little more rich due to position relative to fuel in the rail. Tuning pulse width can get them more even as well as careful gapping.

Hello everyone!
Im new on this site!

Usually a light brown or tan color on the white insulator indicates proper temperature - not too rich or lean.

Thank's!...

Acutally it means nothing to that effect.

Its called a corona effect and its caused by vapors and things under the hood being attracted to the porcelin. Also known as flash over.

its ultimately caused by oil in the air under the hood and does not harm the way the spark plug performs.


Jason Norwood
NGK Tech support