Problems with Mercedes A Class: Black smoke, loss of engine power and strong exhaust odor

Hi, your problem reminds me a lot of a problem I had with my Mercedes A Class (built in 2012, petrol engine) - another variant, the B Class, also has similar problems. I'm not a mechanic, but a car enthusiast with a little experience. I noticed the same symptoms with my car. After some back and forth, I took it to my trusted garage. After some time on the lift, they discovered that the defect in one of the lambda sensors was causing my car to stop running properly. The replacement was relatively expensive, costing me 375 euros, but afterwards the car ran like new. No more smoke, no more strange smells. Could you perhaps tell us a bit more about your vehicle? For example, how old it is, how many kilometers it has run, etc. That will help me to give you better advice.

(Translated from German)

Hi, thanks for the quick reply. That sounds like the solution to my problem! My A Class now has 56461 km on the clock, the last service was about 6 months ago. Was hoping the last service would fix it, but apparently not. I will have the lambda sensors checked! Hopefully that will fix my problem. Your info was really helpful, thanks again!

(Translated from German)

Hey, no problem, that's what we're here for, to help each other! Your A-Class doesn't have that many kilometers on the clock yet, which is good. I think you're on the right track by having the lambda sensors checked. Even if it's expensive, it could solve your problem and the black smoke and smell will most likely disappear. For me, this was the solution and I haven't had these problems since. I would also definitely recommend that you visit your garage again and discuss the problem. They know your car well and can give you the best advice. Even if it can sometimes be expensive, some unexpected problems can only be fixed by experts. Hopefully this information will help you and you will soon find a solution to your problem. Good luck and have a safe journey!

(Translated from German)

Many thanks for the advice, especially for the detailed experience with the lambda sensor. It's reassuring to know that I'm not alone with this problem. I will definitely point out the lambda sensors to my mechanic and hopefully that will make the whole exhaust plume disappear. Thanks again for your help, I really appreciate it. With your info I am now better equipped to tackle this problem. I will keep you posted! Drive safe and have a great day!

(Translated from German)

Hi guys need some help, I have a 2006 Mercedes S500 W221 LWB with 144,000 miles on the clock, I've been having to clear fault codes on mainly longish runs on the motorway I've been getting all sorts of crazy fault codes like, after exhaust treatment faults and noticed a significant loss of power and this is obviously dangerous when it suddenly happens going along the motorway but once I've cleared the issues the car comes back with full power and my mpg drops back to normal levels.......any help would great

It sounds like you're dealing with a complex issue. Given the variety of fault codes and the sudden loss of power, it could be related to the fuel system, exhaust system, or even the engine control unit. However, it's hard to pinpoint without more information. I would recommend having a professional mechanic perform a thorough diagnostic check. This is a safety-relevant issue, especially when driving on the motorway, so it's important to have it checked as soon as possible. Please keep us updated on your progress. Do you have any other questions or concerns?

I have an A-Class w176 A45 AMG. Sometimes i get the code P0420 but no black smoke or anything crazy. Only minor but really minor stutter in Neutral. Changed the first lambda sensor, second one is fine. I had a lot of trouble with fuel system before but that is all fixed, new injectors, spark plugs, coils everything, new hpfp It says efficiency of cat converter. Is my cat coming to an end! Because i was already planning on changing to catless