So car was misfiring 2 weeks back and giving a p0304 code. Changed the spark plugs and it worked fine until this week when it started again but worse, giving a p0302 code. Naturally tried changing the coil packs but made zero difference.
When I was changing them I noticed this plug (see below) has almost completely melted through. Could someone tell me please what this is/does please and if it could cause my symptoms? Thanks
![](https://i.ibb.co/t3hVbz4/20190625-173626.jpg)
Zoomed out...
![](https://i.ibb.co/B3Vt92Y/20190625-173630.jpg)