Contour Enthusiasts Group Archives Forums General Troubleshooting Fighting another misfire---different

The carbon track is coming up the porcelain (near the center electrode in the combustion chamber). I'm sure there is a name for tha area, but you know what I mean. It seems very erratic, no plug seems to track on every change. Also, I do get a CEL every now and then on the highway after passing cars and whatnot. The code indicates a lean condition on one bank, and the plugs show that too, they are abnormally white.

Right, I know that is the problem, but I can't understand why it continues to carbon track. Also, would that cause backfiring into the intake? Could a fill up of bad gas have caused the worsened conditions this time and it might go back to it's normal mis next fill up? Thanks again.