From my experience he reason the coils are bad is because the plugs are so worn out and the gap on the plug has degraded terribly. I started noticing a misfire at just about 100k miles, mainly while under load (which makes sense because the plug is working harder under a load).
Turns out, i had a coil that cracked/exploded, ive never seen a coil do this before. The cause of the coil going bad from the spark plug caused a backfeed to my pcm; in turn ruining my pcm.
I decided to change just that coil and plug. BAD IDEA!
3 months later.. misfire on another cylinder. Luckily it was just the plug, but while i was in there, i replaced all the plugs!
Its hard to say that the likelyhood of a bad coil will cause the PCM to be damaged each time... but from my experience and already having it happen once, it's probably more common than we think. Also reading the amount of people who have had similar experiences, i tend to think its more likely than not. When it comes to electronics, i tend to believe that anything is possible.
At the very very least, change every spark plug right NOW! do not wait for a bigger issue!
It took me about an hour to change all 6 spark plugs. Me and the father in law, used MACBWT's youtube video and it was a breeze! It is not hard, just a bit tedious. Following his video and you will be fine! It will save you a lot of $$$.
Edited by addisonm06, 16 October 2017 - 04:00 PM.