oxygen sensor hole thread tap

I need to clean the oxygen sensor hole threads up on a 85 2.8 mpfi. I believe a 3/4-16 tap will work but I'm not sure. Any ideas?

Thanks

Take a shot, sounds like all you can do is mess it up worse right?

Someone said it's a18mm hole, the same size as a large spark plug and a spark plug thread chasing tool will work.

Thanks

it is metric thread, the same as a plug in most cases.