Anyone know what would cause the ceramic to bust in half? These plugs have been in the car since i got it which was 1yr and 30k miles ago. It recently has been misfiring bad so I checked them and this is what I found on plug #1. They are bosch platium +4’s btw, but i’m putting ngk v powers in now.
I should also mention that i did advance the timing to 17-18 degrees a couple weeks ago when i put a rebuilt distributer in.
TIA.