Re: multiple cylinder misfire
To be a little more specific, it will flash during a catalyst damaging misfire. If it's picking up a minor misfire it will just turn the check engine light on, a larger misfire or multiple misfires which can damage the cats in a short period of time will cause it to flash. Not trying to step on your toes, just adding a little more info.
Originally Posted by BeaterXJ
BTT, what type of plugs did you put in it? I don't want to start a spark plug war, but I absolutely hate Champion spark plugs. Which I also believe is what Jeep is still putting in from the factory. If you put in Champions I would try a different plug first before changing $200 coils. I've always had great luck with NGK's in anything. Autolites also seem to work in a wide variety of vehicles without any problems.
It's been a while since I've taken a coil rail off but I believe there are some rubber boots that go between the coil rail and the spark plugs. On most coil on plug systems you can remove these and replace them separately. If that's the case I would recommend replacing those as well, if they are bad they can cause the spark to jump from the coil to the cylinder head instead of going through the spark plug causing a misfire. Hope that helps!
When advice is always free just remember, you get what you pay for!