2009 n/a r56 with 170,000 miles. I’ve had this car for 4 months, I daily drive it 120 miles a day, and have taken it on road trips multiple times with minimal to no issues (brake servicing). But, this mini has the most stubborn 1st cyl misfire in the world. Runs smooth on a cold start but after it gets to operating temp it pulls the P0301 and the idle turns really rough, and you can hear popping from the intake. First, replaced all spark plugs and the 1st cyl coil. Still misfired. Checked for vacuum leak, still misfires. Noticed more oil consumption than usual, so went on to the VCG. When I opened everything up for the gasket, I noticed a piece of the tensioner broken, so I sent it to a friends shop for a timing chain job. Timing was off 2 clicks and thought that after the fix it would be good to go. Checked compression when it’s cold and when it’s at operating temp and it’s a little high, but doesn’t waver.

But of course, still the most stubborn 1st cyl misfire on the planet. Called a local garage that only works on mini’s to get their advice, the shop owner told me that gen2’s can be finicky with coils and plugs and gave me some part numbers. Expensive is the only word I have for that, but I got them any way and popped them in this morning. Still the same, smooth cold but rough misfires in cyl1 when it warms up. The friend that owns a garage is quick to say that my cylinder took damage when the timing was bad and that I need a new head. This being a high mileage 11 year old vehicle, I’d rather not just jump into another 2,000 dollar repair. Gonna see if I can get it in early next week for diag at the mini shop I mentioned, but I’m the mean time does anyone have any outlook on this? I’ve read through some threads with similar issues but in cyl3 and everyone was saying it might be a vanos issue.

thanks for any input guys, I’d rather not go upside down on this car but I love the thing.
edit: also pulled p0100 MAF sensor code when test driving today as well

 

Have you pulled the head to check the valves or scoped it?

 

No I haven’t, trying to rule everything else out that I can.

 

You said you have good compression, have you done a leak down test?... doubt you have a bent valve if your compression tests are coming back good. Unless miraculously your valve is stuck sealed. I assume you have transfered coil from cylinder #2 to #1 and seen if the code mis fire follows.

 

I did swap coil from cyl 2 into cyl 1 and still had the same issues. I haven’t done a leak down test, and if my mechanic did then he didn’t mention it (which is not probable) but I did get a slot for a diag on Monday at that mini specialty shop in my city. A lot of these threads I’ve seen people talk about carbon build up and vanos issues so hoping I’ll get answers after this new shop takes a look.

 

The car has 170K miles, I bet it's due to carbon build up on the intake valves. I've seen cars start losing compression and running rough at around 120K miles. You can try the walnut blasting, but since it's already losing compression, it may not fully correct the issue like a full cylinder head rebuild. Basically a rebuild will clean the valves and cylinder head, replace the valve seals, make sure the valves seal correctly, then reassemble. That's pretty good that you got 170K miles out of it. The project isn't as bad as it sounds.
A bore scope (available from Amazon for cheap) down the intake manifold will confirm.

 

no one mentioned fuel injector!