Failing Turbo Causes Multiple Issues in Audi Q8

I had nearly identical issues with my 2019 Audi Q7 TDI last summer. With some experience working on turbocharged engines, I recognized the symptoms you described as potential boost pressure control problems. The inconsistent MAP sensor readings combined with the whistling noise and power loss pointed to a wastegate valve defect. The turbocharger wasnt properly regulating boost pressure, causing the engine management system to reduce power output as a protective measure. My workshop diagnosed it using specialized diagnostic equipment to monitor the boost pressure and intercooler system. The wastegate valve had developed internal wear, preventing proper boost control. They replaced the faulty wastegate assembly and recalibrated the system. Total cost was 860 Euro including parts and labor. The repair completely resolved the symptoms, no more check engine light, normal power restored, and fuel consumption returned to standard levels. To help diagnose your specific case, could you share: Current mileage, Any previous turbocharger-related repairs, Whether symptoms get worse under specific conditions, If you notice any black smoke from exhaust, Full error codes from your OBD scanner This information would help determine if youre dealing with the same wastegate issue or potentially something else in the boost control system.

Thanks for the feedback on the wastegate issue. My car has 47083 KM and just had its annual service last month. The pressure sensor readings from my OBD scanner show P0299 and P0234 codes, which seems to align with your diagnosis. The symptoms definitely get worse under heavy acceleration, and the check engine light flashes more frequently during those moments. I notice the power loss is particularly bad when the intercooler would be under high load, like during highway merging. The MAP sensor data is all over the place, sometimes showing normal boost, other times dropping to near zero. No black smoke from the exhaust though. Based on your experience, it sounds like I should expect a similar repair cost. Will book it in for diagnosis.

Thanks for providing those additional details. The error codes P0299 (underboost) and P0234 (overboost) together with the inconsistent MAP readings strongly suggest a failing wastegate actuator, just like in my case. The symptoms matching worse under load is typical for this issue, when the turbocharger needs precise boost pressure control the most, the faulty wastegate cant maintain proper pressure. This causes the turbo lag and power loss you described. The absence of black smoke is actually good news, as it suggests the turbocharger itself is likely still in good condition. In my repair, the core turbocharger components were fine, it was just the wastegate mechanism that needed replacement. With similar mileage and symptoms to what I experienced, youre likely looking at the same repair. The throttle body and intercooler systems should be checked during diagnosis too, but based on the matching pattern, I expect theyll find the wastegate as the primary issue. Given current parts costs, you should budget around 800-900 Euro for the complete repair. Make sure they perform a full check of the boost pressure system after installation to ensure proper calibration.

Thank you everyone for the helpful input. Just wanted to update that I scheduled the car for diagnosis next week. The symptoms match exactly what was described, especially the correlation between turbo lag and boost pressure issues under heavy load. The OBD codes definitely seem to point toward a wastegate problem rather than a full turbocharger failure. Having consistent pressure sensor readings would be a relief, as the current sporadic MAP data makes the car pretty unpredictable to drive. Will set aside around 900 Euro for the repair based on the feedback. Really hoping its just the wastegate actuator and not more extensive turbocharger damage. Will update once I get the official diagnosis and repair completed.