VW Polo Exhaust Leak Causes Cabin Fumes & Power Loss

I had a very similar issue with my 2006 VW Golf 1.4L last winter. With some experience working on VWs, the symptoms you describe match exactly what I encountered, engine light, poor performance, and exhaust odors. In my case, the issue turned out to be a faulty lambda sensor (also known as oxygen sensor). These sensors monitor exhaust gases and help regulate the fuel mixture. When they fail, they cause the exact symptoms you describe, poor running, lack of power, and that distinct exhaust smell. My local workshop diagnosed it with their diagnostic computer, and the replacement including labor came to 375€. The repair completely resolved the rough running and restored normal performance. Before committing to repairs, it would help to know: Current mileage on your Polo, Any recent repairs or maintenance, Whether the engine light is steady or flashing, If the engine management system shows any stored fault codes While a failing oxygen sensor is common on these engines, the symptoms could also indicate other exhaust system issues. Having the proper diagnostic scan will pinpoint whether its the sensor or possibly something more serious with the catalytic converter. If you notice the engine gets worse during acceleration, getting this checked soon is important, as running with a malfunctioning sensor can lead to increased fuel consumption and potential catalytic converter damage.

Last service was done at 141966km and included a full inspection. Just did a diagnostic scan yesterday showing P0135 code, which points to the oxygen sensor circuit malfunction mentioned. Pretty sure this confirms the initial suspicion about the O2 sensor being the culprit. The engine light stays steady and performance definitely drops when accelerating uphill. Tried cleaning around the exhaust manifold thinking there might be an exhaust leak, but the rough running persists. Sounds like replacing the NOx sensors might be the next logical step before looking at more expensive components like the catalytic converter.

As mentioned in my previous reply about my Golf, that P0135 code is exactly what I encountered. The steady engine light combined with poor uphill performance matches my experience perfectly. After getting the NOx sensors replaced on my car, all symptoms disappeared. The rough running and exhaust smell were completely resolved. I initially considered a DEF fluid issue or exhaust pipe problem, but the diagnostic code pointed clearly to the sensor malfunction. The timing is interesting, my sensor failed around the same mileage range. Its a common wear point for these VW engines. While cleaning the exhaust components was worth trying, these sensors typically need complete replacement when they fail. Since youve confirmed the fault code matches the oxygen sensor circuit malfunction, you can likely skip checking the catalytic converter for now. The repair cost should be similar to what I paid (375€), and its much more cost-effective than replacing other exhaust system components unnecessarily. Just make sure to use OEM or high-quality sensors, I learned that cheaper alternatives often lead to the same issues returning within months. The engine light and performance issues should clear up immediately after replacement.

Thanks for clarifying about the P0135 code, that definitely aligns with the O2 sensor issue you identified. Good to hear the repair costs should be reasonable compared to a full catalytic converter replacement. Ill go ahead and book it in for the sensor replacement next week, focusing on getting OEM parts to avoid future problems. The steady engine light and performance issues match exactly what others experienced. The particulate filter and rest of the exhaust system got checked during my last service, so Im confident were targeting the right component with the NOx sensor replacement. Ill report back once the repair is done to confirm if it resolved the rough running and exhaust smell like it did in your case. Really appreciate the detailed advice and sharing your similar experience, helped avoid potentially expensive diagnostic work on other components.