VW Touran Rough Running + Exhaust Leak Fix Guide

I had a similar issue with my 2005 VW Golf, also with a gasoline engine. Based on my experience with exhaust systems, what you describe sounds very familiar. The check engine light came on and I noticed rough engine performance, especially during acceleration. There was also a noticeable exhaust leak smell getting into the cabin. After scanning the engine codes, it turned out the lambda sensor (oxygen sensor) was defective, causing incorrect fuel mixture readings. The repair involved replacing the faulty lambda sensor and checking all exhaust pipe connections. The total cost came to 375€, including parts and labor. Since the fix, the engine has been running smoothly and the exhaust leak smell completely disappeared. However, to provide more specific guidance for your case, could you share: Have you had the engine codes scanned? Is the rough running constant or only during acceleration? Where exactly are you noticing the exhaust fumes, front, middle, or rear of the vehicle? Any unusual noises from the exhaust system? These details would help determine if your issue matches what I experienced or if there might be other components involved.

Thanks for your input. My mileage is currently at 65632km since the last service 3 months ago. I did get the codes scanned at a local shop. It showed P0420 and P0135, which points to potential issues with the exhaust pipe system and oxygen sensors. The rough running is most noticeable during acceleration, and the exhaust fumes seem strongest around the middle section of the car. There is also a distinct rattling noise coming from underneath, especially when cold. I checked underneath and noticed one of the exhaust pipe brackets looks pretty rusty. Would it make sense to replace both the sensors and the mounting brackets? Just trying to avoid multiple trips to the workshop while keeping repair costs reasonable. The engine light staying on is really starting to worry me.

Based on those diagnostic codes and what you describe, your situation sounds even more similar to what I experienced with my Golf. The P0420 in my case also indicated a catalytic converter efficiency issue, while P0135 pointed to the oxygen sensor malfunction. The rattling you mention is concerning, in my case, the rusty brackets caused the exhaust system to hang lower than normal, creating stress on other components. This actually contributed to damaging the oxygen sensor connections. I would strongly recommend addressing both issues together. My mechanic explained that a faulty oxygen sensor can cause improper fuel mixture, leading to catalytic converter damage if left unchecked. The NOx sensors also play a crucial role in the exhaust treatment system, and their readings can be affected by loose mounting brackets. When I had mine fixed, they ended up: Replacing both oxygen sensors, Installing new mounting brackets, Checking the EGR valve operation, Testing the catalytic converter efficiency Total cost was around 550€, but it prevented more expensive repairs later. The rough running and exhaust smell disappeared completely after the repair. The continuous engine light definitely warrants immediate attention, waiting too long could lead to more extensive exhaust treatment malfunction and potentially damage other components.

Thanks for the detailed explanation. Those part replacement costs and diagnostic details really help. The symptoms do align perfectly with what I am experiencing. I will schedule a repair visit this week to get both the sensors and brackets replaced. It makes sense to fix everything at once, especially since the exhaust pipe brackets are already showing severe rust. The continuous engine light and those error codes definitely suggest I should not wait any longer. My main concern was that the catalytic converter might need replacement, which would have been much more expensive. But from what you described, addressing the oxygen sensors and mounting hardware should resolve the rough running and exhaust leak issues. Just to confirm, after your repairs, did the engine light clear immediately? Also wondering if the shop needed to order any special parts, or if these components are typically in stock? Want to make sure I can get this sorted in one visit since the exhaust fumes are becoming quite bothersome.