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Engine & DrivetrainDiscussions about the engine and drivetrain of your vehicle.
This is a discussion thread titled "Spark Plug Question", within the Engine & Drivetrain forum, part of the Technical & Vehicle Assistance Forums category.
The brown/orange color discoloration on the upper porcelain insulator (where brand and p/n is). Is it an indication of any problem (assuming everything else is normal)?
are they both the same heat range plug? looks like boot just stained insulator? was boot hard to come off or melted a tad on the end where it's discolored? plug on the rt looks like it might not be specd for truck or is the left one OEM? also center electrode worn bad on one side on the rt plug.
This discoloration is caused by compression leakage blowing carbon past the shrink seal between the porcelain and the steel ( during plug production, the steel is heated then pressed around the porcelain, upon cooling the steel shrinks for a tighter seal). What you are seeing is carbon deposited on the insulator. The band stops where the boot seals. Most likely you will see carbon on the bottom of the boot as well. Turbo/Super charged engines make this problem worse as there is more cylinder pressure. It is common for the specified plugs for these engine types to be specially designed and have better sealing properties. I use the Denso OE plugs myself and rarely see leakage, and if so, only one or two plugs from a set. NGK plugs are not bad for sealing either.
If you see the carbon band extend upward into the boot, inspect/clean or replace the boot as carbon is conductive and can eventually cause spark leakage down the inside of the boot resulting in boot damage and misfire.
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Spark Plug Question
Linear Mode
