Misfire codes keep triggering on 2003 Vic
I'm a newbie from IL. I was recommended to this site from Crownvic.net....
I have a 2003 Crown Victoria P71 (Cop car).
The car has had all coils replaced at about 65k miles, and it presently has 80k. The car started to run rough and I had a code of cylinder 3 misfire. I replaced the coil and it ran fine for about 50 miles. Then, at a long stop light while the car is in drive, it was running great but after about 5 minutes, there was a shutter of the engine, and then the Check Engine light came on. When I checked the code, it was a bad coil and misfire on cylinder 4. I replaced the coil in 4, and it runs great now, but if I sit at a light in drive, after about 3 minutes, it starts to run rough. Once I start going for a block, it runs great again. If I don't stop, or stop for a minute, the car runs fine. Any ideas?
The plug wells are dry. The boots are dry. We have not had any wet weather, being in the heart of winter in Chicago.
I appreciate the help.