Adventures in Mechanics
Me: Goodyear said your plug gaps were way too wide a couple months ago, so I suppose I'll have a look.
She: There's nothing wrong with my car, it's running fine.
Me: Yeah, I know there are no symptoms at the moment, but I trust Jeff and if he says there's a problem, I'm going to look at it. Besides, I'm curious about how it's doing, and plugs make good indicators.
She: If you insist, but there's nothing wrong with it.
Okay, so it's got an aluminum head and the last thing I feel like doing on a Sunday is boring and installing Helicoils, so I do it cold and pull the plugs very carefully. It's a Contour 2 liter four banger, so they are ridiculously easy to get to, right square on top center. The boots are about three inches long, but they come off with no real problems. (Yeah, I know. Twist and pull gently, not by the wire.)
Jeff was correct, but didn't tell the whole story. Even after only 40,000 miles, the electrodes are worn badly. Initial gaps too wide can do that, but these are still the factory plugs, so <shrug.> I gap the new ones to .0050 and carefully install, making sure to use dielectric lube in the boots. Fire it up and after an initial shudder like the computer is saying "whoa, something new here", it runs great. Even has about 10 more horsies on the seat-o-pants meter.
Two days later, she comes home.
She: I don't know what you did, but my car runs like crap, and the check engine light is on. Why did you even mess with it?
Me: Because...never mind, I'll have a look.
Idles smooth as silk, and no hesitation traversing the throttle slowly through low speed into higher RPMs. So I road test. Sure enough, the idiot light is on, and it's bucking like a don't come knocking trailer. Read the code, and it's a misfire detection on number 3.
Yeah, you guessed it. Stupid brittle wire fracture that didn't burn open until later, and fails under high compression only. Installed new plug wires.
Me: Okay, it's fixed.
She: Yeah okay, I'll believe that when I see it. I don't know why you had to mess with it anyway. Next time, let Jeff do it.
Now, Jeff's a nice guy and competent enough, but I've done in-frame overhauls that ran forever, and he's not up there. But now I'm the guy that fixes stuff that ain't broken, and screws up on even simple jobs. I hate it when that happens.