Car: 2002 Base, 5 speed, 216,000
A couple months ago started getting a P303 code (#3cyl misfire) started doing some research and here is what I have done.
1. Seafoam still had P303
2. New plugs, still code.
3. New wires, still code.
4. New coil pack, still code.
5. New OEM injector, still code.
Done some more research and it was recommended to preform leak down test.
6. Had a leak down test preformed by a BMW shop in town, results were that I had ether valve guides worn or burnt valve. Bought a remand cyl head from Dover Cyl Head in GA. and had it installed. Problem solved, so I thought it has been over 2 months since I had the work done and no code, The other day check engine light back on checked code P303 car is back to missing. I will start the car and acts like it is only running on 3 cylinders but after driving it seems to clear up. Can shut off car and restart and misfire is back.
I M stumped

 

Sounds like your local shop has a comeback (warranty). Take it back and have them fix it. They'll likely recheck the basics and perform another compression and/or leakdown.

 

I've had the same issue, although recurring on an irregular basis. I can go for a couple months or more with no light and then it seems the light will pop every time I drive the car. 2011 R55 with 185K so far, I swapped coils and plugs between #3 and #4, reset the light to see if the problem traveled or remained on #3 (which it eventually did). No issues with performance, engine does not stall or sputter, no impact on fuel economy. Ran Seafoam through the tank as well as spray though the throttle body. Leakdown showed possible leak on #3 intake valve, but that was easily 25-30K ago and still going strong. Really don't want to spend $2K plus for a valve issue, if that's what it is.