I have read this same problem in other places including here. My girlfriend has 2003 focus se (single overhead cam) It started off by running rough and idling funny almost to where it stalls. Accelerating is slow. Took to a shop to check the engine light code and it said that cylinder 2 is misfiring and the coil pack is bad. I replaced the spark plugs, plug wires and the igintion coil and it is still running the same. You can hear it mis firing. Any ideas what else it could be? Does anybody know the cylinder numbers? I figured it was cylinder one starting from the passenger side on down to 4 closest to the coil is that correct? Need help quick! Sorry for not searching but didn't have time.

 

Did you check the distributor cap, or just the plain or distributor itself? May be that the distributor is malfunctioning. Whenever you wanna check the ignition system dont forget to check the distributor also.

 

First off, you don't have a distributor, you have a coil pack. The ECU tells it to fire the coil for each cylinder. When you removed the plugs, were any of them fouled? If you had a miss, then it should show on the spark plug. They would look wet or darker than the others. The cylinders are numbered from 1 to 4 from the passenger side to the driver. If you replace the coil, not all coils are number correctly for this motor. Just did one of these last week and ran into that. If it doesn't run right, see if your local ford dealer can get you a picture of the coil's firing order. I know that they are numbered, but that doesn't mean they are right. I have worked on fords at the dealership level. for years. Not everything in books is gospel.