VW Arteon: Exhaust Leak & Rough Engine Symptoms Fix

As someone with some car repair experience, I had a similar issue with my 2018 VW Passat last year. The symptoms you describe match exactly what I experienced, rough running engine, engine light, and that distinct exhaust smell. After taking it to my regular workshop, they diagnosed a faulty lambda sensor that was causing incorrect fuel mixture readings. This triggered the engine light and caused the rough running. The exhaust smell was actually coming from an exhaust leak where the lambda sensor connects to the exhaust system. The total repair came to 375€, which included the new sensor, labor, and fixing the small exhaust leak. After the repair, all symptoms disappeared and the engine ran smoothly again. Before jumping to conclusions about the catalytic converter, which would be much more expensive, it would help to know: What engine size does your Arteon have? Have you noticed any decrease in fuel efficiency? Does the engine light stay on constantly or does it flicker? Are there any other warning lights showing up? Have you had any recent exhaust work done? These details would help determine if you are facing the same lambda sensor issue or if it might be something different like the catalytic converter or NOx sensors.

Last service was done at 108000km and they checked all sensors, no issues found back then. Since the EGR valve and catalytic converter were verified during service, I would lean towards your lambda sensor theory. The exhaust leak smell has gotten stronger lately, especially when the engine is cold. My engine light stays on constantly, no flickering. Fuel efficiency dropped about 15% in the last month. The repair cost you mentioned seems reasonable if it turns out to be the same issue. Was your lambda sensor repair done with OEM parts? Also wondering if the exhaust leak at the sensor connection point caused any damage to surrounding components that needed additional repair?

Thanks for those extra details. Based on what you described, especially the constant engine light and increased fuel consumption, it does sound very similar to my lambda sensor situation. In my case, I initially went with an OEM lambda sensor since these components can be sensitive. The exhaust leak at the sensor mounting point had created some carbon buildup and minor corrosion around the threads, but luckily no significant damage to the surrounding exhaust pipe or catalytic converter. One thing I noticed after fixing the lambda sensor was that my particulate filter performance improved significantly. The faulty sensor was causing incorrect fuel mixture, which had started to affect the DPF regeneration cycles. The workshop also found that the exhaust leak had slightly affected one of the NOx sensors readings, but cleaning the sensor solved this without needing replacement. This might be worth checking in your case too, given the similar symptoms. Some suggestions from my experience: Get it checked soon, as exhaust leaks can worsen quickly, Request inspection of the sensor mounting threads for corrosion, Have them verify all exhaust connections while its on the lift, Make sure they check the sensor wiring harness too My total repair stayed at 375€, but prices for parts might have changed since then. The most important thing is fixing it promptly before it affects other components in the exhaust system.

Thanks for this detailed feedback about the lambda sensor repair. Based on all these details, I will schedule an appointment this week. My main concern was spending a lot on catalytic converter replacement if that turned out to be the issue, but the lambda sensor problem seems to match my symptoms exactly. The constant engine light and recent fuel efficiency drop you mentioned experiencing are identical to what I am seeing. Good point about checking the mounting threads and connections, I will make sure to ask them to inspect those areas thoroughly, especially since my exhaust smell is worse when cold. I will request they also check the NOx sensors and particulate filter while diagnosing the issue. From what you described about your repair cost and process, this seems like a much more manageable fix than I initially feared. Will get it looked at before any additional exhaust system damage can occur.