VW Lupo Owner Reports Major Exhaust & Engine Issues

I experienced a similar malfunction with my 2004 VW Polo, which shares many components with the Lupo. As someone with moderate experience working on VWs, I initially noticed the same symptoms, rough idle, engine light, and exhaust issues. The workshop diagnosed a faulty lambda sensor, which was causing incorrect fuel mixture readings and the subsequent poor engine performance. The exhaust leak you mentioned could be related, but might also be a separate issue requiring attention. My repair cost was 375€ including parts and labor. These symptoms often indicate multiple potential issues: Lambda sensor failure, Damaged exhaust manifold gasket, Corroded exhaust pipes, Catalytic converter problems To provide more specific guidance, could you share: Current mileage, Engine size (1.0, 1.4, etc.), Any recent repairs or maintenance, Exact location of the exhaust leak, Any additional warning lights besides the engine light The exhaust leak allowing fumes into the cabin is concerning and should be addressed immediately for safety reasons. My workshop found that the lambda sensor replacement resolved the performance issues, but your leak might require additional repairs.

Thanks for sharing your experience with lambda sensors. In my case, I had my last service about 6 weeks ago which included oil change and basic inspection. During diagnostics, the catalytic converter was flagged as potentially failing, showing reduced flow rates. The engine light started appearing intermittently before becoming constant. A visual inspection revealed significant corrosion around the exhaust manifold connections. There is a visible gap where the exhaust pipe meets the manifold, which explains the fumes. The EGR valve was also tested and showed irregular readings. Given these symptoms match what you described, I will have the workshop check both the lambda sensor and manifold gasket. The quoted repair estimate is around 850€ for all components including labor.

Thanks for the additional details. Your situation sounds more complex than what I initially encountered with my Polo. When my lambda sensor failed, I also noticed the exhaust leak was actually coming from a corroded manifold section, similar to what you described. The combination of lambda sensor issues and exhaust leaks often points to a chain reaction of component failures. The EGR valve irregularities you mentioned are particularly telling, in my case, the faulty oxygen sensor readings were causing the EGR system to malfunction, creating a domino effect of issues. The 850€ quote seems reasonable considering the scope of work. When I had my manifold gasket replaced along with the oxygen sensor, the total was close to that. The workshop found that the exhaust leak had actually contributed to premature catalyst wear in my case. One suggestion based on my experience: have them inspect the entire exhaust system while its being worked on. My initial repair missed some developing issues that could have been caught early, ultimately leading to additional repairs a few months later. The reduced flow rates in your catalytic converter could be directly related to the exhaust leak causing incorrect readings. Once the exhaust leak is fixed, you might find the catalyst is actually functioning properly.

Thanks for the input. After getting my car checked today, the diagnosis confirmed several issues. The oxygen sensor and EGR valve both need replacement, plus the exhaust manifold gasket is completely shot. The mechanic found the NOx sensors are also showing error codes. The good news is the catalytic converter seems okay after further testing, the flow issues were indeed caused by the exhaust leak affecting sensor readings. The total repair cost came to 780€, slightly better than the initial quote. They will replace all faulty components and reseal the exhaust pipe connections tomorrow. Really appreciate the advice about checking the entire exhaust system. The inspection revealed some early signs of corrosion in other areas that we can monitor. Will update once everything is fixed and running.