Ive had this same problem for the past 4 of the five years that I have had the car. Its my baby. My daily driver. Well any ways this problem seems to get worse and worse to the point that now its bugging me.

For some reason after driving for about 20 min 15 miles or so the car will start to give me random misfire and then all of a sudden the check engine comes on. If I stop, shut it off and start it back up the cel goes away only this time for only like five minutes.

When the cel comes on the the misfire gets worse any ideas

 

Have you thought to pull the code that it's throwing so then you can actually diagnose the issue?

 

missfire may be caused by a bad distributor rotor or cap (the first thing i would check)