Black smoke and power loss in BMW 1 Series gasoline engine: NOx catalytic converter efficiency questionable

Hey! I had something similar with my BMW 3 series, it's an older model (just a few years younger). The last time it was in the shop they had to do some work. Mainly we had a problem with the fuel system, which had the same symptoms as yours. We also had to have the engine rebuilt a bit. The soot you mention indicates incomplete combustion. That's definitely a serious problem. It's important to get it checked as soon as possible, otherwise you risk further damage to your vehicle. Have you ever checked the lambda sensor? This can sometimes trigger an error message. To be honest, it sounds like a lean mixture problem to me. A characteristic of this is a strong exhaust smell and a loss of power. If the catalytic converter has covered many kilometers, its efficiency can decrease. Have it checked at the garage, it could be these things. Hope that helps! Good luck buddy!

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Thanks for the detailed reply, that sounds like a lot of trouble. So it was also a problem with the fuel system and the engine in your case, I see. I haven't checked the lambda sensor yet, but I will definitely do that. What I'm particularly interested in, do you happen to remember how much you ended up paying for the repair? And did any other problems arise after the workshop visit or have you noticed anything different since then? Thanks again and best regards!

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Moin Moin, sure, no problem! The repair costs are of course always a big factor. In my case, the total cost of repairing the NOx catalytic converter was €1550. Not cheap at all, I tell you, but probably necessary if the thing is outdated or heavily loaded. So reckon with similar costs for your BMW 1 Series. Since the workshop visit, my old car has actually been running like clockwork again and the problem with the low efficiency of the NOx catalytic converter has been solved. It's running like Schmitz's cat again! No further problems have arisen so far. So the few bucks were well invested. Sometimes you just have to bite the bullet and fork out a little more to get the car running smoothly again. Good luck with your visit to the garage and hopefully you'll be able to keep the costs down. Best regards back!

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Thank you very much for the helpful information, really! Your experience sounds very encouraging, despite the high repair costs. But you're right, sometimes you just have to dig deep into your pockets to make sure the car runs properly again. I think it's now time to take my BMW to the garage, I'm now much better informed about what I might be facing. I hope the cost remains similar to yours and that the problem is finally resolved. Thanks again for your great advice! Hopefully my car will run like Schmitz's cat again afterwards! Have a nice day and all the best!

(Translated from German)

Servus, The problem with NOX faults is not unknown in this vehicle or in these model years. The NOX catalytic converters are often sulphurized due to short journeys. If the system is generally in order the NOX catalytic converter can be regenerated in a similar way to a DPF or, in this case, desulphurized. However, the NOX sensor (looks like a lambda sensor with electronics) is often defective and must be replaced. However, only buy original spare parts, otherwise the joy will not last very long!

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