Have you seen this before?

[VNSSMAN]

My car has had its check engine warning light on for awhile and the local mechanic has racked his brain trying to fix it with certain things. He said being at 98000klm you could replace the spark plugs. It had a slight wobble in the engine at idle, So if figured alright i will do it. Never again as its a bitch to get to that bolt far right standing from the front of the vehicle. Anyway the sprark plug closest to that bolt looks like this

[mmcalaisv]

What car/engine is this from??
Most likely though this is caused by water running down into the spark plug well.
If it is the rear plug then it is probably coming from excess water dripping down from the windscreen area.
How well does your scuttle panel seal against the windscreen?

[VNSSMAN]

The car is a VE omega, I did think maybe it was a build up of water sitting close to the seal an finding it's way in. I have a new spark in and just left it but made sure the seal was tight and well the best that I could see and feel closed off to any more water building up. I have checked windscreen washoffs and all other things that may lead to water getting in there again but would you think its worth getting cleaned out or checked by dealer who then may say oh yeh we need to replace that looking just at the $$$