Audi S1 NOx Sensor Issues Causing Exhaust Leaks

I had a similar issue with my 2013 Audi S3. As someone with moderate experience working on cars, I initially thought it might be more serious when the check engine light appeared. The emission sensor readings were off, and like yours, the engine felt sluggish. After checking the diagnostic codes, my workshop found that the nitrogen oxide sensor had a faulty connection, basically just a loose cable and plug connection to the component. The repair was straightforward and cost 95 Euro, including diagnostic time. The interesting part was how this simple connection issue affected both the air-fuel ratio readings and overall engine performance. Once fixed, the engine response returned to normal, and the exhaust leak disappeared completely. Before suggesting more specific solutions, could you share: Current mileage on your S1? Are you getting any specific error codes? Have you noticed any changes in fuel consumption? When was your last catalytic converter service? These details would help determine if your case is similar to what I experienced or if there might be other underlying issues to address.

Thanks for your detailed response. Just had my car serviced last week at 196739 KM. The diagnostic showed error code P0130, pointing to the exhaust system and pollution control components. My fuel consumption increased by about 2L/100km since the issue started. The NOx sensor seems to be the likely culprit, as the symptoms match what you described, especially the engine responsiveness issues. The catalytic converter was inspected during my last service and appeared to be functioning properly, but there might be a connection between the sensor failure and its performance. Good to hear your repair was straightforward. Planning to take it to the workshop tomorrow to get a proper diagnosis and hopefully a quick fix like yours.

Based on the error code P0130 and symptoms you described, this sounds very similar to what I experienced with my S3. The increased fuel consumption matches exactly what happened with my car before the repair, it was also around 2L/100km higher than normal. After seeing your mileage reading, its worth mentioning that NOx sensors typically start showing issues around the 180000-200000 km mark, so the timing fits. The connection between the NOx sensor and catalytic converter performance is crucial, even a partially malfunctioning sensor can throw off the air-fuel ratio, leading to decreased efficiency and higher fuel consumption. In my case, while the initial diagnosis pointed to a simple connection issue, the workshop found that the sensor itself had degraded. The complete sensor replacement ended up costing 320 Euro, but it resolved all issues: Fuel consumption returned to normal, Engine responsiveness improved immediately, Exhaust leaks stopped, Check engine light cleared The entire pollution control system works better now, and the catalytic converter efficiency improved once the correct sensor readings were restored. Make sure the workshop checks all connections in the exhaust system while they have it up on the lift, sometimes there are related issues that need addressing.

The exhaust system issue sounds exactly like what I was worried about, and your repair experience matches my symptoms perfectly. The connection between the emission sensor and overall engine performance makes total sense now. My situation with increased fuel consumption and reduced engine response seems to align with your case. Given that my car has similar mileage to when your issues occurred, Im prepared for the possibility of a complete sensor replacement rather than just a connection fix. The 320 Euro cost for a new NOx sensor is actually better than I expected. Good point about having them inspect the entire exhaust system while checking the pollution control components. Will definitely request a thorough check of all connections when I take it in tomorrow. Really appreciate you sharing the specific improvements you saw after the repair. It gives me confidence that fixing the sensor should resolve all my current issues, from the fuel consumption to the check engine light and engine performance problems.