VW Polo TDI: Power Loss & Rough Running Issues Fixed

I had a very similar issue with my VW Golf TDI 2017. As someone with some experience working on diesel engines, these symptoms immediately pointed to injection problems. The rough running, power loss, and check engine light are classic signs of a faulty injector. After seeing these symptoms, I took it to a specialized diesel workshop where they diagnosed a defective injection valve that was causing an inconsistent air-fuel ratio. The repair involved: Complete diagnostic testing, Removal and testing of all injectors, Replacement of one faulty injector, Recalibration of the injection system Total cost was 515€, including parts and labor. The repair completely resolved the issues, no more jerking, stalling, or check engine lights. Before suggesting more specific solutions, could you share: Current mileage on your Polo, Whether you notice any black smoke from exhaust, If the problems started suddenly or developed gradually, Recent fuel quality or filling station changes, Any recent maintenance performed These details would help determine if your symptoms match what I experienced with the injection system. The throttle body and intake manifold should also be inspected, as carbon buildup can cause similar symptoms in TDI engines.

Latest service was 2 weeks ago at 117694km. The black smoke started appearing gradually over the last month. Always used premium diesel from the same station. Since the mass airflow sensor affects the air-fuel ratio, and the garage checked the oxygen sensor during service, I am wondering if we can exclude these parts from potential issues. I want to verify if anyone else successfully fixed similar symptoms by addressing injection-related problems before proceeding with repairs. The rough running seems worse in cold weather, which might support the injection theory.

Thanks for providing those details. My Golf had very similar symptoms at around 120000km, and the injection issue diagnosis proved correct. The correlation with cold weather you mentioned is particularly telling, I noticed the same pattern before getting my injector replaced. Since your oxygen sensor and mass airflow sensor have been checked, and you are using quality fuel, this further points to the fuel injection system. In my case, the faulty injector was causing incorrect air-fuel ratio despite having good sensor readings. A few observations from my experience: The black smoke gradually appearing matches exactly what happened with my Golf, Premium diesel usage means contamination is less likely the cause, Cold weather sensitivity often indicates injection timing issues, Recent service rules out basic maintenance problems The catalytic converter was initially suspected in my case, but testing revealed the root cause was indeed the injector. The repair resolved both the performance issues and the black smoke problem. Consider requesting a specific injection system diagnostic. The repair cost might be similar to what I paid (515€), but it is worth it given how completely it resolved the issues. Since you have the same symptoms I had, down to the cold weather correlation, I am fairly confident you are dealing with a similar injector problem.

I appreciate the detailed insights about the injector problems. The cold weather correlation and similar mileage point make a lot of sense, and having the oxygen sensor and mass airflow sensor checked during service helps narrow down the possibilities. The black smoke issue starting gradually matches the injection system theory, and since I use premium diesel, fuel quality likely isnt the cause. Knowing that your repair completely fixed similar symptoms on a similar vehicle gives me more confidence about pursuing the injection system diagnosis. I will schedule a diagnostic specifically focused on the fuel injection system and have them inspect the injectors. The 515€ repair cost seems reasonable considering the comprehensive fix it provided in your case. Since our symptoms align so closely, especially with the cold weather sensitivity and rough running, I feel more confident this is the right direction to investigate. Will update once I get the diagnostic results and hopefully confirm if its indeed an injector causing these issues. Thanks for sharing your experience, it really helped clarify the next steps I should take.