Dear Car Talk:
Recently, my son-in-law's 2005 Acura 3.2 began to misfire. While changing the spark plugs, the end of the "coil on plug" wire for spark plug No. 3 came off, leaving the coil in my hand and the broken spark plug inside the head. I finally succeeded in removing it piece by piece by working at it with a flat-head screwdriver and a pair of long-nosed pliers. It took three days to get it all out. After it was all removed, we replaced the plug and coil/wire combination, and the car runs fine.
My question: Do the coils break like this often? Should they be replaced periodically?
Dan, I like the way you say that the top of the coil "came off," rather than saying, "I broke it off." You definitely have a future in management!
We actually do see this once in a while in the garage, and it's caused by intense heat in the cylinder-head area, multiplied by lots of time.
So if these "coil on plug" spark-plug wires (where each contains a coil for that specific spark plug) sit there for a decade or so, the heat can "fuse" them to the tops of the spark plugs. Then, when you try to remove them to change the plugs, you end up breaking off the top of the plug and having to dig out the remains. I trust you're now familiar with this procedure, Dan.
At this point, the other coils themselves don't need to be replaced; they could be good for years. But it does make sense to (carefully) try to remove them -- just to make sure you can.
You may want to schedule this one plug at a time, Dan -- over the next five holiday weekends.
Once you have that coil and wire off, remove the plug and see what it looks like. If it looks fine, you can put it back in there.
But before you put the spark-plug wire back on, do what we do and apply some dielectric grease. Dielectric grease is a non-conductive lubricant that can handle the intense temperatures under the hood, and hopefully prevent the rubber and plastic of the spark-plug wire from melting and cementing itself to the porcelain of the plug.
So next time, you'll be able to get your spark-plug changes down to a day and a half. Good luck, Dan.