VW Fox Diesel: Crankshaft Sync Issues Drain Fuel Economy

As someone with moderate car repair experience, I had a very similar issue with my 2013 VW Polo diesel. The symptoms you describe match exactly what I experienced, engine warning light, poor performance, and increased fuel consumption. The crankshaft sensor was indeed the culprit. This sensor is crucial for engine synchronization, working together with the camshaft to maintain proper timing. When it starts failing, it causes exactly these symptoms because the engine control unit receives incorrect position data. I took it to a workshop where they confirmed the diagnosis with proper testing equipment. The total repair came to 340€, including parts and labor. The fix made a noticeable difference, engine response improved immediately and fuel consumption returned to normal. Before suggesting more specific advice, could you share: Have you noticed any rough idling? Does the problem get worse when the engine is warm? What error codes came up in the initial scan? Has the timing belt been replaced recently? These details would help determine if your issue is identical to what I experienced. The reference value readings from your scan would also be helpful to compare against typical sensor readings.

Just had my last service at 85000km and they didnt spot any issues. The engine does get really rough when idling, especially after warming up. Getting error code P0335 on the scanner which points to the crank sensor circuit. Starting to think its more than just a sensor issue since the timing chain was never replaced during my ownership. Appreciate the detailed response, its helping me narrow down the problem. The way the misfire happens especially during acceleration makes me suspect its time for a proper timing chain service too. Pretty sure the previous owner skipped some maintenance given the service history gaps I found.

Thanks for the additional details, those symptoms align even more closely with what I experienced. After my crank sensor issue was fixed, I actually ended up needing a timing chain replacement shortly after, which suggests the two issues were related. The P0335 code along with rough idling and misfires during acceleration strongly indicates a timing chain problem in addition to the crankshaft sensor issue. In my case, the worn timing chain was causing inconsistent camshaft timing, which affected the crankshaft position readings. I had both repairs done, first the sensor, then about 2 months later the complete timing chain service when the problems partially returned. The total ended up around 1200€ for the timing chain job, but it completely resolved the misfire issues and restored proper engine performance. Would definitely recommend getting both checked since: The timing chain has never been replaced, Service history is incomplete, Misfires are present during acceleration, Engine runs rough at idle when warm These symptoms match classic signs of both a failing crank sensor and timing chain wear, which can cause similar synchronization problems between the crankshaft and camshaft.

Thanks for breaking this down so clearly. The symptoms definitely seem more complex than I initially thought. Finally took it to a trusted workshop yesterday and they confirmed both issues, worn timing chain and faulty crank sensor. The timing chain was showing significant wear and the engine synchronization was off, explaining the misfires during acceleration. Going ahead with both repairs next week. They quoted 1350€ total which seems fair based on what others paid. At least now I know why the engine was behaving so poorly. Will make sure to keep better maintenance records going forward and not skip the timing system service intervals like the previous owner did. Really glad I asked here before just replacing the sensor alone, as that would have been a temporary fix at best. The complete timing chain service should sort out all the rough running issues and prevent further camshaft timing problems.