Mini Roadster Diesel Engine Running Rich

That sounds awfully familiar! I had a similar experience with my Mini. It started with reduced engine power and rough running, and then the check engine light came on. I also noticed my fuel economy had gone down the drain. Have you checked your air filter? A clogged filter can sometimes cause a rich mixture, but I suspect your issue might be more serious, like mine was. It could be a faulty oxygen sensor fooling the engine computer, or perhaps even the fuel injectors themselves. I hope it is nothing too expensive.

Thank you for your reply. My Mini Roadster is indeed showing similar symptoms to what you describe. I have not yet checked the air filter, but will do so immediately. When you experienced this issue, did you also notice any jerking when accelerating? And how did you eventually resolve the problem?

Yes, I did experience jerking during acceleration, especially at lower speeds. It was quite annoying. In my case, it turned out to be a faulty fuel injector. The mechanic diagnosed it using some sort of diagnostic tool that read the engine codes. Honestly, I wouldn't recommend trying to fix this yourself unless you're very experienced. The fuel system is quite sensitive. I'd suggest taking it to a reputable workshop to have it properly diagnosed.

I wanted to thank you for sharing your experience. It does seem my Mini Roadster is suffering from a similar issue. The workshop confirmed today that one of the fuel injectors was defective. They'll replace it, and the repair should cost around 515€. Hopefully, this will resolve the rich mixture problem.