This is the weirdest thing, but 3 times now, and the last time the plugs were installed by the dealer, (who accused me of breaking them as I was installing them, like THAT could happen) my Zetec ATX runs fine until I turn the a/c on, then it starts stumbling, missing and bucking. When I pull the plugs there is always 1 or 2 that are broken. The insulator is cracked all the way from the top to the bottom. And there are carbon blow-out marks along the crack, where obviously the electrical spark is leaving the plug. The first two times the dealer said I did it as I was installing them incorrectly, but the last time I said "OK, YOU install the plugs after you put it on the diagnostic scope". So they did, and it ran fine, for 5 days. Yesterday I hit the a/c switch, and it immediately started missing slightly, but the time I got it the 20 miles I drive home, it would barely run. And finally, fianally, I got a CEL. But I know exactly what is wrong, I know the plugs will be cracked. The dealer said it was not possible for that to happen, obviously he's wrong, but what does ? I have NEVER in my life heard of this happening. It looks like there's been 20 million volts run through the plugs, the crack is big, and very black. And yet the car checked out fine on the diagnostic tool. What the ??????????
