In Reply to: frozen spark plug posted by ralph hildebrandt on January 04, 2001 at 18:24:24:
With the engine warm but not too hot, sometimes they'll come out with an impact whench on it's VERY LOWEST! setting. The vibration will help loosen it. Soak the plug recess with WD40 or some such penetrant first. At the first indication of loosening, stop & finish removing with a hand wrench. No. 5 will present a quite a feat just getting at it with the right combo swivels/universals & socket extensions. A 90 air ratchet will reach fine but may not rattle it enough but would try that first. If it does loosen for you, unscrew it back & forth in 1/8 or less turn increments to "rock" it out, using more penetrant. If the threads end up getting trashed, you can tap & install a thread repair insert in-place without pulling the head, with a shop-vac in blow mode duct taped to the exhaust and cyl 5 just past bdc on the power stroke to blow any chips out of the sparkplug hole while you work.
Lead-base antisieze can kill an O2 sensor & mess up the catalytic converter so use sparingly & not near the tip of the sparkplug. Good luck!