Replaced the spark plugs today, car is a 2007 xj8 with 96,000 miles, car was running good, good mpg, and good performance but thought it was due time to change them, everything went well found the right rear plug a bit of a fiddle . the old plugs were in very good condition, gap was same as new plugs, the old plugs were identical in appearance in so far the electrode on them was a light grey, Dont ask me to post a picture, I am too old to know how to do that, my aching bones can attest to that, it will take a few days to get over this little exercise,
regards
Dave

 

Hi Dave,

Well done. They can be a pain to do. I have an early version of the x350 and there are no access panels to reach the back cylinders so it took over a day to get mine replaced. I had to remove the rear housings for the brake fluid and the cabin air filter housing to be able to get to the cylinder 7 and 8. To remove the housings the windscreen housing needs to be almost removed. To remove that you the windscreen wipers also have to be removed. Total pain.

I also had the problem of a new spark plug splitting once I had fitted it and when I started the car it broke in half and left the threaded portion in the cylinder ! At least you didn't have that nightmare.

My spark plugs appear to have not been changed for over 130K miles so that is why I changed mine. I also had a misfire which is why I changed them but it made no difference to the misfire which I still have. I think they might have been the originals.

Thanks,

Chris

 

"I also had a misfire which is why I changed them but it made no difference to the misfire which I still have. I think they might have been the originals."

Probably a coil-scan for a code or replace a coil until misfire cured.