Re: 5.4 sparkplug replacement
I did mine at 80,000 miles and didn't break any. I ran GM top engine cleaner through the intake small hose 3 times. 1/3 of the can one day, let it cool, ran another 1/3 and once more the next day. Then when the engine was still a little warm I loosened the plugs 1/8 turn and sprayed PB blaster down the holes. After 15 min., I removed them slowly sometimes turning them back and forth. If you hear a kind of rubbing sound, then you're alright. If no noise, you may have a broken end. I put the original type in but Champion makes a one piece plug. I'm not fond of Champions so I went with the original. If one breaks, the best tool is the Lisle #65600.