Iv been beating my head off the wall on this #4 coil. Iv replaced it 4 times over the last year. I think I cured it for good. Locating the problem just above it. Leaky heater hose. It leaks just enough to short out the coil and not enough to show a leak on the ground or any where else. After extensive review of this problem and thanks to a few posting its cured. Double claming the hose and replacing the coil and wrapping it with a home made boot to protect it. I used a High Temp rubberized cloth material and wrapped the upper portion of the coil extending it down about three inches past the wire connector. Then I Zip tied it to prevent leakage at that end to. I also used High Temp RTV to seal the wires in the connector to prevent moisture from getting in. And don’t be afraid of greasing the plugins too. This worked so well I’m going to repeat it on the other 7 coils since I blew 2 other coils out about six month ago on a nice rainy day. I replaced them at the time but now I’m going to go back and mod them.