BMW X1 Rough Running + Failed Emissions: Common Fix Inside

Hi there! I have some experience working on cars and had a very similar issue with my 2020 BMW X3 last year. Actually, my also went through this with his BMW X2. Just dealt with those exact same symptoms, rough engine, sluggish response, nasty exhaust smell and that dreaded check engine light. Turned out my lambda sensor (oxygen sensor) was shot. Got it fixed at my regular workshop for about 375 Euro, parts and labor included. Car's been running like new since then. Before jumping to conclusions though, could you share: How many miles/kilometers on your X1? Any other warning lights besides the check engine? Notice if fuel consumption has increased? This will help confirm if you're dealing with the same issue I had. These symptoms can sometimes point to different problems in the exhaust system.

Thanks for your input! My X1 just hit 25444 KM and had its latest service done. No other warning lights apart from the check engine light. Now that you mention it, I have noticed the fuel consumption has gotten worse over the past few weeks. Your lambda sensor experience sounds pretty similar to what I'm dealing with. Really helpful to know the rough cost too, might save me from a heart attack when I get the bill! Did you notice any immediate difference in performance after the repair?

Hey again! Yes, the difference after replacing the lambda sensor was like night and day on my X3! The rough running and sluggish acceleration disappeared immediately after the repair. The fuel consumption went back to normal within about two tank fills, dropped from using nearly 15% more fuel back to standard consumption. Since your symptoms and situation are so similar to what I experienced, I'm even more convinced it's the same issue. The mileage on your X1 is actually pretty close to when mine started acting up too (mine was around 27000 KM). Just a heads up, when my mechanic replaced the sensor, he mentioned these can sometimes fail due to poor fuel quality or minor oil contamination. Since then, I've been more particular about where I fuel up and keeping an eye on oil levels. Quick tip though, if you're heading to get it fixed, try to book it in soon. I made the mistake of driving around with the issue for a couple weeks, and it didn't do my catalytic converter any favors. Better to get it sorted before it causes any downstream problems. Let me know how it goes when you get it checked out. Always curious to hear if others' experiences match up with mine!

Thanks so much for all the detailed info! Really glad I asked here before going to the shop. I'll definitely get it looked at ASAP, don't want to risk damaging the catalytic converter. Smart advice about the fuel quality too, I've been pretty unusual about where I fill up lately. Just booked it in for tomorrow morning actually. The mechanic I spoke to over the phone also thought it sounds like a lambda sensor issue, so your experience has made me feel a lot more confident about what to expect. Will definitely be more selective about fuel stations going forward too. Thanks again for taking the time to share your experience, this kind of real-world feedback is exactly what I was hoping for. I'll update here once it's fixed to let you know if it was indeed the same problem. Really hoping for that night and day difference you mentioned!