02 Taurus idles rough

I have had the dealer look at it and they replaced one plug twice saying it had some carbon problem. (never heard of it and I work on cars for fun) Still had problem so they wanted to replace all the plugs. Did it myself and saved $100. It still does it but much worse now that it is raining. I just put dielectric goo on boots except for the one plug I can't get to right now. Seems to work but want to know if the coil pack could be the problem. Sounds just like an old cracked distributor would when it is wet out. Can a coiil pack get a crack and do the same thing? I haven't driven the car yet, put the goo on while I am here at work and won't drive it untill tomorrow morning. Just want to know if coil packs can go bad that soon.

My friend's Escape did the same thing last week and it was a coil pack, after only 45k miles. The Check Engine light is supposed to come on when the engine is misfiring, but hers didn't for a couple of days and only did after it got so bad the truck would stall at a stop. Hope this helps and good luck!