Mini Cooper Diesel Performance Issues

Whoa, sounds familiar! I had almost the exact same thing happen with my Cooper, though mine is a petrol version. Check engine light, felt like I was towing a boat, and the fuel consumption was atrocious. It turned out to be the manifold pressure sensor, one of those pesky car sensors that causes all sorts of chaos when it goes bad. Have you checked for any obvious vacuum leaks? That can definitely throw things off.

Yeah, I've poked around a bit, but didn't spot anything obvious. When yours went, did it throw any specific codes? Or was it just generally running rough? Was it obvious the manifold sensor was broken?

Mine was definitely the manifold pressure sensor. Honestly, I didn't get too deep into the diagnostics myself I just took it to a trusted mechanic. They plugged it in, saw the codes pointing to the sensor, and confirmed it with some further testing. It's worth getting it properly diagnosed, but yeah, based on your symptoms, I'd bet good money on it. It's a pain, but at least it's a relatively cheap fix compared to some other automotive sensor failures.

Just wanted to close the loop on this. Took it to the shop, and you nailed it faulty manifold sensor. They found a large vacuum leakage which was likely the root cause. New manifold sensor and 235€ later, she's running like a champ again. Thanks for the heads-up!