This chump is stumped. Prepping for my 150K service on my 2010 XC70. I let the dealer do 90% of the work unless it is simple wrench or if the labor costs are painful. i.e. To replace the hatchback strucks was going to be super painful if the dealer did it but I found a YouTube video and successfully did it myself. Anyway, the dealer was going to change out the sparkplugs but it seemed like that was something I could do. So, I bought the Volvo plugs for $75 (6cyl) and went home to change them out. I was very methodical about removing and replacing and adding a tad of anti-seize grease to the new plugs. I put everything back in and it won't completely fire up. I tried adjust the tightness of the new plugs 3 times to no avail. So, then I thought I would put the old plugs in and see if that worked. nope. I was triple extra methodical in then putting the new plugs in again. It won't completely fire up. Any ideas?