Replaced #4 coil and problem is solved so far. I bought 8 new coils so I have 7 left if I have that problem in the future.

 

Well, if it were me, I'd install all but one of the new ones and leave just one old coil in. Then if the problem occurs again, chances are you know exactly which one it is and you can use one of the unused old ones as a replacement. Repeat six more times until you're left with the last new one. :-)

 

That's such a good idea I should have thought of it.