VW Polo Turbo Issues: Boost Sensor Warning Signs

I had almost identical symptoms with my VW Golf 2003 diesel. The engine light came on, and the turbo system was acting up with similar power loss issues. Having some experience with turbo-related problems, I first suspected the boost sensor. The main symptoms matched yours exactly: poor acceleration, whistling noises, and that annoying check engine light. After a thorough diagnostic, it turned out the pressure sensor wasnt actually faulty, it was just a loose connection in the wiring harness to the boost sensor. The workshop found that the cable connector to the turbo boost sensor had corroded and wasnt making proper contact. They cleaned the connection points and secured the plug properly. Total cost was 95€ including diagnostic time. This fixed all the symptoms and the engine light went off. Before suggesting more specific solutions, could you share: Have you checked for diagnostic trouble codes? When was the last time you had a turbo system service? Does the whistling noise change with engine RPM? What kind of fuel economy drop are you seeing exactly? These details would help determine if youre dealing with the same issue or if theres something else going on with your turbo system.

Thanks for the detailed input. After checking the diagnostic codes yesterday (P0299 and P0234), the boost-related codes confirm my suspicions about the intake manifold and turbo system issues. The whistling noise does vary with RPM and gets louder above 2000rpm. Fuel economy has dropped from 5.2L/100km to around 7.5L/100km. The pressure sensor connection point check you mentioned is really helpful, will have that examined first since its the least expensive fix. Last service was actually 2 months ago at 127000km but they did not check the turbo system specifically. Will get the wiring harness and boost sensor connections inspected based on your experience before considering a full sensor replacement.

Thanks for the update on those diagnostic codes. Based on those readings and the symptoms, I think youre dealing with something more complex than what I faced with my Golf. P0299 and P0234 together typically indicate a boost leak somewhere in the turbocharger system, rather than just a sensor issue. While cleaning the boost pressure sensor connections might help, the significant drop in fuel economy and those specific codes suggest you might have a physical leak in the turbo system. Common spots to check include: Intercooler hoses and clamps, Turbo inlet pipe connections, Vacuum lines connected to the turbo actuator, Wastegate operation and seating With my Golf, once the simple fix of the sensor connection didnt fully resolve similar issues, I discovered a split in one of the intercooler hoses that was causing a major boost leak. The complete repair including new hoses and clamps cost around 280€. Given your recent service history and these specific symptoms, I strongly recommend getting a boost leak test done. This will pinpoint exactly where your turbo system is losing pressure, saving you from replacing parts unnecessarily.

Thanks for sharing those diagnostic findings. Going from 5.2L/100km to 7.5L/100km is quite a jump. Good call on taking a measured approach with checking the pressure sensor connections first. The check engine codes definitely align with a turbo system issue. Based on your description of the whistling changing with RPM and the fuel consumption increase, a boost leak test seems like the smart next step before replacing any parts. Will check all the points you suggested, intercooler hoses, connections, and the intake manifold components. Makes sense to start with the simpler fixes first. If the connections look good but the issues persist, at least we know to focus on potential physical leaks in the turbo system rather than sensor problems. I appreciate the detailed breakdown of what to investigate. Will update once the boost leak test results are in and we figure out whether its just loose connections or something more significant in the turbo system.