2009 Mini Cooper Cabrio (R57)

Several weeks ago, my CEL came on while driving. I am able to hook up my laptop to the OBD-II port and use OBD Auto Doctor software to retrieve codes and monitor things. The only code reported is P0303. My car has 76k miles, so I ordered new plugs and coils and installed them. The code persists - I have tried erasing the codes via my OBD software, and by disconnecting the battery for awhile.

While replacing the plugs, I noticed oil in the spark plug wells, so I bought a new valve cover gasket set and installed that. I also dumped a bottle of Chevron Techron in my fuel tank. Changed the oil and filter, cleaned the cam position sensors. I've only put a few miles on the car since all of this.

When I first hooked up my laptop weeks ago, I saw 30-40 misfires per cylinder (weighted moving average for prior driving cycles). Now, it shows 1 misfire (weighted moving average for previous driving cycles) for cylinders 1, 3, and 4, and zero misfires for the current driving cycle. Those numbers have gotten much better, but my CEL is still on.

Not sure what else to try at this point. Want to avoid the walnut blasting of the valves until I know I need to.

Thanks for listening...

 

Forgot to mention that after installing the new plugs and coils, I then switched coils #2 and #3, but I still got P0303 - the misfire didn't move with the coils. Then I swapped plugs #2 and #3. Misfire stayed on cylinder #3. I also did the dollar bill test with the exhaust - no issue there, so I assume I don't have a bad valve or piston.

 

Check the following:
1- Fuel pressure.
2- (let the car run for 5min to warm up) then remove all spark plugs and do a compression test. What are the numbers?
3- if compression numbers are within 10psi of each other, move to the next step which is swapping fuel injectors.

 

Solved it... went to the local O'Reilly's and borrowed their OBD-II tool to erase the codes. I guess my software wasn't erasing them properly. Weird. Thanks!