03ESPro

I pulled one of the plugs on my 03 ES today just for kicks, and while the electrode looked fine, I noticed discoloration on the ceramic where it meets the metal. Is this normal? I've never noticed it on any of my other cars before, and it almost looked like scorch marks. Here's a pic of it.

Roddimus Prime

just heating up....high cylinder temps. Just replace them and you'll be fine.

macdaddyslomo

yeah keep in mind Mazda's run rich...more fuel = higher temps....they look fine though

Crazy365

Click here to view this usefull Common Spark Plug Conditions Picture Chart.

juddz

Hey, 03ESPro -
That light brown stain that you see above the metal shell on the insulator is known as a "corona" stain. This is not an issue. Basically, the air around this portion of the plug becomes ionized (positively charged) and attracts oil particles from the air, which creates the stain that you see. This is not a sign that the spark plug is discharging across the insulator to the outside of the shell, and it is also not indicative of any internal leakage.

03ESPro

Thanks juddz, like I said, I've never seen it happen before on any of my other cars. But if what you say is true, most of them have been V6's or V8's and the plugs have not been in a small enclosed area like our 4 bangers, so it probably wouldn't happen with better air circulation.

Tom Slick

try using the "macro" function on your camera for close up shots like that. your camera should either say "macro" or have a picture of a flower to indicate the macro function. you'll get clear close ups with it.