VW Tiguan Rough Running + Exhaust Leak Symptoms Fix

I dealt with very similar symptoms on my 2011 VW Golf 2.0 TSI last winter. Having some experience with exhaust system issues, those symptoms immediately pointed to sensor problems in my mind. The engine light came on and I noticed the same rough running and exhaust leak sounds. The exhaust fumes smell was particularly noticeable when idling. After checking with my regular workshop, they diagnosed a faulty lambda sensor (oxygen sensor) that was causing incorrect fuel mixture readings. The total repair came to 375€ including parts and labor. Since having it fixed, the engine runs smoothly again and all the symptoms disappeared. The exhaust leak sound was actually related to the sensor causing improper combustion rather than a physical leak in the system. To provide more specific advice for your case, could you share: Any scan tool error codes you might have? Does the rough running happen more at idle or during acceleration? Have you noticed any changes in fuel consumption? Has the catalytic converter been replaced before? These details would help determine if your issue is indeed similar to what I experienced or if it might be something else in the exhaust system.

My car was last serviced at 112000km and they didnt spot any issues back then. After scanning the car with an OBD reader, I got P0171 and P0507 error codes. The rough running is most noticeable during idle and fuel consumption has increased by about 15% in the last month. The catalytic converter is original. The rough running and exhaust fumes seem worse on cold starts, and the malfunction indicator light now stays on permanently. The exhaust leak sound is quite noticeable from the front of the engine bay. The particulate filter was replaced about 40000km ago, so that should still be fine. Based on your experience, it does sound similar to your oxygen sensor issue. Really hoping its not the manifold as that would be significantly more expensive to fix.

Thanks for providing those details. Given the error codes and symptoms you described, this does sound very similar to what I experienced with my Golf TSI, but with a few concerning differences. P0171 indicates a lean fuel mixture and P0507 points to idle control issues, which matches perfectly with the rough idle youre experiencing. In my case, when the oxygen sensor failed, it also caused similar lean running conditions. However, the exhaust leak sound from the engine bay area is concerning. While my oxygen sensor issue caused some odd noises, they werent specifically from the front. This could indicate an exhaust manifold crack, which unfortunately is a known weak point on these engines. My suggestion would be to: 1. Get the oxygen sensor tested first since its the cheaper fix at around 375€ 2. Have them check the manifold for cracks while theyre at it 3. Verify the NOx sensors are functioning correctly, as they can cause similar symptoms The good news is your particulate filter being relatively new rules out at least one expensive potential cause. The increased fuel consumption and cold start issues are classic symptoms of exhaust system problems, but could be caused by either the sensor malfunction or a manifold leak. Would be helpful to know if the exhaust leak sound changes with engine temperature or remains constant?

Thank you for the clarification. The exhaust leak sound definitely gets quieter as the engine warms up, but never completely goes away. I noticed its most prominent during the first 5 minutes after a cold start. I have booked the car in for next week and will definitely ask them to check both the oxygen sensor and inspect the manifold for cracks. The EGR valve is also due for cleaning according to my service schedule, so might get that done at the same time since they will be working in that area anyway. The fuel consumption increase is getting quite expensive, so hopefully they can sort it quickly. The workshop quoted 2 hours labor plus parts for the oxygen sensor replacement, which sounds about right compared to your experience. They mentioned a manifold replacement would be considerably more, around 1200€ if needed. I will update once I know what the actual issue was. Really hoping its just the sensor like in your case rather than a cracked manifold. Thanks for sharing your experience, it has helped me better understand what to expect.