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Black smoke and power loss in a 2006 BMW 3 Series: experience with NOx catalytic converter repairs

Hello friends, I'm worried about my 2006 BMW 3 series gasoline engine, which has ~238k km on it. When accelerating it smokes black and the "Check Engine" light is on. I have also noticed that it is losing power, and a strange noise that sounds like an exhaust leak. I also can't miss a strong exhaust smell. My first guess is that something is wrong with the NOx catalytic converter and the efficiency is too low. Does anyone know the problem and have experience of repairing it? Especially after my last experience with my trusted mechanic, I've become a bit more cautious. What was your experience if you had something like this and had it done in the workshop? Thanks in advance for your help!

(Translated from German)

4 comment(s)

Hey, I had a similar problem with my 2009 BMW 5 series gasoline engine, which now has over 200k km on the clock. I also noticed that it smoked black when accelerating and the "Check Engine" light was always on. There was also a constant loss of power. It then turned out to be a similar problem to yours - it was the catalytic converter and it had to be completely replaced. All I can say is that this was a pretty serious problem, so I would strongly recommend taking your car to the garage as soon as possible and having it checked thoroughly. - the consequences can be far reaching if this isn't fixed early. I also had to have the catalytic converter changed on my BMW 5 Series, which was quite a job. Hope this helps you. Have a safe journey!

(Translated from German)

Hi, thank you very much for your reply! Your case sounds pretty similar to mine, and now I'm seriously worried. I'm already planning a workshop visit for my BMW 3 series. How much did it cost when you had the catalytic converter changed? Have you had any other problems since then or did the car run as normal afterwards? Thanks for your help!

(Translated from German)

Hey, sure, no problem! I'm glad I can help. Well, I went straight to my mechanic after the same problems occurred. The result was that the efficiency of the NOx catalytic converter was too low. I had to have the incorrect readings due to a defective NOx sensor repaired, which cost me €665. It's a hefty sum, but since the repair the car has been running like clockwork again, so I can't complain. So don't panic, just go to the garage and have it checked. It hasn't been a problem for me since then and the grinder is purring again! I hope that reassures you a little. Have a good trip!

(Translated from German)

Hello, thank you very much for your helpful information! It all sounds like quite a lot of work, but I have now made an appointment at the garage. The price of €665 is hefty, but if the repair makes the car run great again, it's probably worth it. I'm reassured to hear that your BMW ran smoothly afterwards. I hope mine will be the same. Thanks again for your help and have a safe journey!

(Translated from German)

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