VW Bora Engine + Exhaust Issues Point to O2 Sensor

I had a very similar issue with my 2004 VW Golf, also with a gasoline engine. From my experience working on VWs, these symptoms typically point to exhaust system problems. The check engine light and rough running were identical to what you describe. After inspection, the workshop found that the lambda sensor (oxygen sensor) was malfunctioning, causing incorrect fuel mixture and triggering the engine light. They also discovered a small exhaust leak near the catalytic converter mounting point. The diagnostic process included: Computer scan for error codes, Visual inspection of the exhaust pipe and connections, Testing lambda sensor signals, Checking catalytic converter function The total repair cost was 375€, which covered the new lambda sensor, labor, and resealing the exhaust connection. To provide more specific guidance, could you share: Current mileage on your Bora, Any recent repairs or maintenance, Whether the exhaust smell is more noticeable at idle or while driving, If the engine performance issues are constant or intermittent Its important not to drive the car extensively in this condition, as a faulty lambda sensor can cause increased fuel consumption and potential catalytic converter damage.

Just had the 50000km service last month and noticed these issues shortly after. Since my garage had it for the service, I wonder if something got overlooked or if its just coincidental timing. Not convinced its just the oxygen sensor since the exhaust smell is quite strong and seems to get worse when the engine warms up. The engine light started flickering before staying on permanently, which makes me think there might be an intermittent EGR valve malfunction alongside the exhaust leak. The rough running is definitely worse when the engine is cold, but the smell persists throughout. I wondered if anyone else experienced issues developing right after routine maintenance?

Having serviced my VW Golf regularly, I can relate to issues appearing after routine maintenance. From your additional details, this sounds very similar to what I experienced, but with a few concerning differences. The flickering check engine light before becoming constant often indicates an EGR valve malfunction rather than just a simple exhaust leak. In my case, carbon buildup in the EGR valve caused intermittent operation, especially during cold starts. The strong exhaust smell getting worse with engine temperature suggests a more significant exhaust leak than what I initially had. My mechanic explained that sometimes removing and reinstalling components during service can stress old gaskets and seals, leading to leaks that werent present before. Key observations from my similar situation: The EGR valve needed cleaning and eventually replacement, Found multiple small exhaust leaks at connection points, Discovered the particulate filter was partially blocked, DEF fluid system needed recalibration after repairs The total fix ended up costing 850€, significantly more than just the lambda sensor replacement. Would strongly recommend getting a smoke test done to pinpoint all potential exhaust leak locations, as there might be multiple issues developing simultaneously. My vehicle showed identical cold-start symptoms, which cleared up completely after addressing both the EGR valve and exhaust leaks.

Thanks for the detailed insights. Pretty sure its more serious than just the oxygen sensor since multiple issues surfaced after the service. Based on your experience, I think I need a thorough inspection rather than just a quick fix. The cold start issues and strong exhaust smell are quite concerning. Ill schedule an appointment with a different workshop to get that smoke test done and have them check the EGR valve. The exhaust pipe connections definitely need inspection, and Id rather catch any catalytic converter problems early before they get worse. The timing with the service seems too coincidental. While 850€ is more than I hoped to spend, it makes sense to fix everything properly now. Would rather avoid any long-term engine damage from running it in this condition. Will update once I get a proper diagnosis from the new workshop.