BMW M4 NOx Catalyst Woes: Real Repair Stories Needed

Hey there! I had a similar issue with my 2018 BMW M3 last summer. The NOx catalyst problem is quite serious as it affects both emissions and performance. When I experienced it, I had the same symptoms, power loss and check engine light. My case required a complete catalyst replacement as it was severely degraded. The repair involved removing the old unit and installing a new OEM catalyst. The job took about 6 hours at the shop. They also found some minor exhaust leaks around the connecting points, which they fixed during the same service. The catalyst isn't just a simple part swap, they need to check the surrounding sensors and exhaust components to ensure there aren't any other issues causing the failure. In my case, they also had to reprogram the engine management system after the replacement. If you're looking for a shop, I'd recommend finding one that specializes in BMW or at least German cars. They'll have the right diagnostic tools and experience with these specific systems. Just keep in mind, this isn't something you want to postpone as it can lead to more engine damage if left unaddressed. Hope this helps.

Thanks for sharing your experience! That's exactly what I'm dealing with right now. Quick question, do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since the fix, or have you noticed any other issues pop up? Really trying to get an idea of what I'm in for here with my M4.

Hey again! Good news, I can actually help with a direct comparison after my repair. The total cost came to 265 € for my M3, which mainly covered fixing the exhaust leak they found. What really made the difference was addressing the NOx storage catalyst aging, that's completely sorted now and the car's running like a dream. Since that repair last summer, I haven't had a single problem with the system. The power is back to normal, no more check engine lights, and the car feels as responsive as ever. It's been super reliable, and honestly, getting it fixed was totally worth every penny. Make sure whoever works on yours checks the whole exhaust system thoroughly, my leak was actually making the NOx catalyst issue seem worse than it was. Once they fixed both problems together, it was like having a different car. Let me know how you get on with yours, always interested to hear how these repairs work out for others with similar BMWs!

Thanks again for all the details! I bit the bullet and took my M4 to a new mechanic yesterday. Turns out you were spot on, they found both the NOx catalyst issue and a small exhaust leak too. What a coincidence! The repair took most of the day, but wow, what a difference! The car feels so much better now, got all its power back and that annoying check engine light is finally gone. Ended up costing me a bit more than your repair, but honestly, seeing how well it's running now, I can't complain. Really glad I asked here first and got your advice about checking the whole exhaust system. You saved me from probably making another frustrating trip to my old mechanic. The new shop did a fantastic job, they even took the time to explain everything they were doing. Thanks again for sharing your experience, it really helped me make the right decision!