I know that you can use a voltmeter to see if the COP is bad (what ohm is good?), but I saw this video and want to know what you think. He pulls the COPs off while the engine is running. Good or bad idea?

 

Not a bad idea for on-site troubleshooting if you don't have a scanner with you. If removing one causes the engine to start acting up, then it's good. The bad one will cause no change to the engine upon removal. I've done this a couple of times when having a misfire while I was out and about.

 

He's pretty brave leaving those bolts up there while starting. My luck they'd have vibrated off and ended up scattered everywhere!

 

I thought the exact same thing! My luck, I would have been fishing those bolts out of the engine!