So don't replace the factory:



With one like this from pep boys:



Or you run into this:


https://www.jaguarforums.com/forum/showthread.php?t=49548

 

XXXType, looking at the plug, can you see what was causing the problem? I would venture to guess that at some point the plug was bounced off the end of the carton, resulting in one of the posts getting bend inward, effectively shorting out the plug, resulting in your dead cylinder. But, I am only going off of a best guess here.

I have used the Bosch +4's on other modern day engines and didn't see anything that would justify their cost.

 

The NGK Iridium plugs work great! No problems what-so-ever.

 

I have been using Bosch+4 in my 99xk8 and I recently replaced them with +2 and the next time I replace them I am going back to the +4. I was using +2 in my 2000 s-type and replaced them with the standard Bosch plug and when I need to change them they will go back to the +2 or +4. I can feel the difference. And that is my .02¢