I get an '04 E-350 with a mil on and skip.
I bring it in and it most likely is a coil or two. It also makes a really wierd squeaking noise, like something is in the right hand cat. Numbers 1 and 3 are flagged on power balance. I remove number 1 and it fails stress test. I move on to number 3 and the coil is funny lookin'. I take it out and it's shorter than the rest and the connector is in the wrong spot. I'm thinkin aftermarket screw up or something. It's a company truck for some HVAC outfit and they need the truck back now and don't want to wait on it.
So me being the nice guy I figured I would put an old coil in that I took out of a junkyard core. But it won't fit in the number 3 hole. It sticks up too far. So I remove the plug but my socket won't fit it. Turns out it's a 9/16 socket. I get the plug out and the damn things a 3v motor spark plug and the coil is also.
Holy shit, some dumb fuck retapped the hole, put the wrong plug in and it broke the hole tip off and embedded it in the piston.
SO now the head and at least one piston (hence the squeaking noise) needs to be replaced. What do they have me do? Cut the end of the plug off so it won't hit the piston anymore, put it back in and send him on his way.
I tell ya I won't ever call this outfit to fix my heating cooling concerns.