I was replacing spark plugs yesterday, and when I put the one of the coils back I noticed it didn't feel like it grabbed the spark plug. It felt OK on the other side. So I took it out again and checked with the spark plug I had just taken out, and sure enough, the socket on the coil isn't as tight as the other one. Looking at the spark plugs, the one that was on that side with the loose fitting coil looks to have a lot more wear than the one that fits well, so I am assuming it wasn't always getting a good spark.
I remember hearing about cracked coils, but not about loose fitting coils. It's easy to miss, because the coil itself fits tight in the spark plug hole, but you should feel some resistance when it goes over the spark plug terminal.
Of course, this had to happen on a Saturday evening (most shops are closed tomorrow, some on Monday too) before I head out on a trip next week. It doesn't look like anybody has these in stock (all the sites I looked at said 5-7 days to ship). So, next time you have the airbox off, check your coils for fit.
Also, anybody have a pair of (good fitting, obviously
) coils he can overnight to me? I'll buy you a new set in return.