Remember, a little brown on the plugs is normal due to the additives that are added to the gas. Usually, the first sign I've seen when these start to let go is the misfire on a hot soak, but not always. Sometimes (it depends on how hot they get), they'll just let go.
Best wishes that this turns out well@!

 

I checked the plugs again and they look okay. I don’t see anything wrong with them. The threads were a little rusty, but that’s to be expected after 80K. The rest was normal. Such a weird problem. Thur & Fri last week it was fine. This morning it was a mess for about 10 mins and was fine after that. No engine light for a week now. I’m just going to keep driving it. Got a coolant system pressure tester, but it doesn’t seem to fit the radiator, nor do any of the adapters. Gotta figure that out and go from there.
Strange thing…that post by “Gabrie” looks a bit like one I posted, but makes no sense. And mine is missing. And I didn’t do it at 1:33 AM.