[v8volvo]

That's a common story. The front 3 plugs are easy to access so they get replaced often. #4 is not as easy, 5 is very tricky and 6 seems almost impossible to most mechanics. Therefore the rear ones essentially never get replaced. The car starts OK most of the summer and fall, but then winter comes and the cold temps finally hit and all of a sudden the engine is dead.

Glad to hear it's running again. Replacing the #6 plug is not that bad if you are patient. I have an 8mm wrench with an S-bend in it that helps to get the nut on the terminal loose, and then you just have to take your time and screw the plug out, going in through the rear belt. If you're really having a hard time, removing the #6 injector makes access much easier so that is a way out if you need it. I'm not surprised it was tough to start with the new plugs in, since the rings were probably pretty gummed up with excess fuel from previous attempts to start by that point. It won't be as difficult next time if it now has 5 good plugs in it, though if #6 plug is dead (very likely it is) it will have a miss at startup.

Congrats on getting it going.