VW Touran TDI Boost Issues Point to Faulty Actuator

I had almost the exact same issue with my 2015 Golf TDI. The symptoms you describe match perfectly with what I experienced, especially the whistling noise and poor throttle response. After some diagnosis, the workshop found that the electrical bypass valve was defective, causing irregular turbo wastegate operation. The turbo actuator wasnt getting proper signals from the pressure sensor, leading to boost control issues. The repair involved replacing the faulty actuator valve and recalibrating the turbo system. Total cost was 250€ and fixed the problem completely. No more whistling, power was restored, and fuel consumption returned to normal. However, before jumping to conclusions, could you share: Any diagnostic codes you might have? Have you noticed any oil leaks around the turbo? Does the whistling noise change with engine temperature? Has the car had any recent turbo-related repairs? With some experience working on TDI engines, I can say these symptoms often point to turbo control issues, but its important to rule out other potential causes. A proper diagnosis with a scan tool would be the best first step. The turbo system is complex and interconnected, what starts as a small issue with one component can affect the whole setup if not addressed promptly.

UPDATE: Just had it diagnosed at last service (2k km ago). The workshop found a significant boost leak where the intercooler connects to the turbo housing. They also noticed the turbo wastegate was sticking intermittently. Repair quote came in at 450€ for parts and labor. The boost pressure sensor was also showing inconsistent readings. Planning to get it fixed next week since the turbocharger issues are getting worse and fuel consumption keeps climbing. My car has slightly lower mileage at 77344km km than yours did when the issue occurred, but symptoms match exactly. Did you experience any warning lights besides the check engine light during your troubles?

The warning lights situation was identical, just the check engine light in my case. Its good you caught the boost leak early, as these issues tend to compound and can potentially damage other turbo system components if left unchecked. The sticking wastegate and intercooler connection leak explain the symptoms perfectly. When I had my actuator fault, the boost pressure was also unstable, causing similar erratic performance. The inconsistent sensor readings you mentioned are likely connected to the boost leak, as the pressure sensor cant get accurate measurements with a compromised system. 450€ sounds reasonable for the scope of work, especially if theyre addressing both the intercooler connection and wastegate issues. For comparison, my repair ended up being lower cost because it was just the actuator, but I later had to fix a boost leak which pushed the total closer to what youre being quoted. One suggestion: while they have the system apart, ask them to inspect the turbo seals and bearings. With the boost leak and wastegate issues, its worth checking for any developing wear that could cause problems later. The fuel consumption will definitely improve once the boost leak is fixed and the turbo system can maintain proper boost pressure again. Keep us updated on the repair results.

Thanks for sharing the diagnostic results from the service. Good to hear they pinpointed those specific issues. The quote of 450€ for fixing both the intercooler connection and turbo wastegate seems fair based on similar repairs I've seen discussed here. The pressure sensor showing inconsistent readings definitely explains the performance issues. My car just had the check engine light during the problems too, no other warning lights appeared. With 77344km on the clock, catching these turbo system issues early should prevent more expensive repairs down the road. The fuel consumption increase was really frustrating for me too, but it returned to normal immediately after the repair. Will update the thread next week after getting everything fixed. Really appreciate the detailed feedback about getting the seals and bearings checked while they have it apart, will definitely ask them to inspect those components during the repair. Hope this helps others who might run into similar boost-related problems with their TDIs in the future. These turbo system issues seem fairly common once the cars get some mileage on them.