I've recently gotten past an automotive headache. I have a 1997 Honda CR-V. Good little car, but has recently developed a bit of a stumble. Figured I'd start with the basics - ignition parts. They were old anyway, so even if not the problem, it's a good maintenance item to do.
Spark plugs usually usually break free then spin out easily. These didn't. I had to fight them out. The first that came out clearly had aluminum smeared on the first couple threads. Not sure what happened there. Same on the next two. They had been in there a while, the gap was way out of spec.
We'll never know what number 4 looked like, because it broke off. The ceramic came out, but left the steel shell behind. Down in the bottom of a hole, about 1 inch in diameter and 5 inches deep....
Well suck. So I ordered Lisle part 65200, a deep hole plug repair kit for that thread size.
I drilled out the old steel shell, then started threading the combination drill tap tool from the kit. Which, once it started engaging, broke off down hole.
So now I've got HSS stuck down there too.
Really didn't want to pull the head, so as a last ditch...
I the broken tap back out by slipping a piece of 1/2 ID cold roll steel tube down there, over the broken tap, and then slipping a 6011 down the middle of that and welding the tube to the broken tap, and turning the whole mess out. I got lucky. HSS does not weld nice. It probably would have cracked apart as it cooled.
I bought a real tap of the appropriate size for the insert and used that to rethread. I'v generally had good luck with Lisle tools, but that kit was terrible.
Cylinder required some cleaning to get chips and debris out. However the car is back on the road, so good enough. Still has the same stumble though.