BMW i3 Hybrid's NOx Issues: Power Loss & Failed Test

Hey there! I experienced something very similar with my 2019 BMW i8 Hybrid last winter at 85k km. The symptoms you're describing match what I went through, engine light, power loss, and failed emissions. The exhaust leak turned out to be more serious than initially thought. When I finally got it checked, there was a cracked manifold causing the exhaust leak, and the NOx catalyst was indeed failing. The catalyst had degraded faster than normal due to the leak allowing excess moisture in the system. These issues can cascade if left unchecked, so I wouldn't wait too long. In my case, they had to replace both the manifold and the catalyst. It was a significant repair, but necessary to prevent further damage to the engine. The car's been running smoothly since then, no power issues or warning lights. Make sure whoever works on it has specific experience with BMW hybrid systems, these aren't your regular exhaust issues, and the diagnostic process needs to be spot-on. Just my two cents based on what I went through.

Thanks for sharing your experience! That's really helpful, as it sounds exactly like what I'm dealing with. Quick question, do you remember roughly how much the whole repair ended up costing you? Also, has everything been running smoothly since the fix, or have you noticed any other issues popping up? I'm trying to get a better idea of what I'm potentially looking at here with my i3. Really appreciate the insight about the manifold and catalyst connection, wasn't aware they could affect each other like that.

Hey again! Glad I could help! After seeing my mechanic last month, it turned out you were spot on about the NOx storage catalyst aging being the main culprit. They discovered and fixed a leak in the exhaust system too, which ended up costing me 265 € in total. Much cheaper than I initially feared! The i8's been running like a dream since the repair, no more warning lights, power issues, or any other problems. The engine response is way better now, and I even notice better fuel efficiency. It really was worth getting it sorted properly. Just keep in mind that these hybrid systems can be tricky, but once you get the right fix, they're super reliable. My car feels just like new now, and I'm already at 95k km. Feel free to ask if you need any other details about the repair. The whole process was pretty straightforward once I found the right mechanic who knew what they were doing with hybrid systems.

Thanks so much, that's actually really reassuring! I bit the bullet and took my i3 to a different mechanic who specializes in hybrids. You were right about everything, they found issues with both the catalyst and a small exhaust leak. The repair was a bit pricier than yours at around 400, but at least it's fixed now. The best part is the car feels completely different, smooth, powerful, and no more warning lights! I should have done this weeks ago instead of stressing about it. The specialist mechanic even gave me some tips about preventive maintenance to avoid similar issues in the future. Can't thank you enough for sharing your experience, it really helped me make the decision to get it properly checked out. Time to enjoy my i3 again without worrying about every little noise or problem! I appreciate everyone's help on this. Case closed!