Audi A8 Turbo Issues: Loss of Power and Whistling

Had a very similar issue with my 2020 Audi A6 TDI. From my experience working on diesel engines, your symptoms strongly suggest a turbo wastegate issue, specifically with the electrical bypass valve. The symptoms match exactly what I encountered, reduced power, whistling noise, and the increased fuel consumption. The boost leak was quite noticeable during acceleration, and the check engine light was persistent. Got it fixed at a workshop where they diagnosed a faulty turbo actuator. The electrical bypass valve was completely defective and needed replacement. Total repair cost was 250 Euro, which included parts and labor. The fix took about 4 hours. Before suggesting specific solutions, could you share: Current mileage on your A8, Any recent maintenance history, Specific error codes from the check engine light, Whether the symptoms appear more during cold starts or when the engine is warm This information would help confirm if your boost control issue matches what I experienced with my A6. These problems are relatively common in this engine family, and knowing the details would help point you in the right direction for repairs.

Thanks for the detailed response. My A8 has 75167 KM and just had its annual service last month. The boost pressure symptoms started appearing right after. The engine codes point to a boost control issue, matching what you described about the actuator valve malfunction. Your experience with the turbo wastegate repair is particularly helpful. The 250 Euro repair cost seems reasonable if it fixes these power delivery issues. Will definitely have the electrical bypass valve checked out since the symptoms align so closely.

Thanks for the follow-up. After fixing my turbo actuator issue, I monitored the car closely and discovered something worth mentioning about post-service problems. The timing of your symptoms appearing after the annual service is interesting, exactly like what happened with my A6. In my case, the workshop found that the turbocharger connections had been disturbed during routine maintenance, which contributed to the actuator fault. Just to compare notes, after my repair was completed, I noticed: Power delivery returned to normal within the first 50km, The whistling noise disappeared completely, Fuel consumption dropped back to standard levels, The turbo system maintained consistent boost pressure The 250 Euro repair has proven cost-effective, as the turbo wastegate has worked flawlessly for 40000km now. Make sure your workshop checks all turbo system connections during the repair, as loose clamps or disturbed fittings can cause similar symptoms even with a new actuator. Would you mind sharing the specific error codes? This could confirm if your turbo actuator fault matches the P0299 code I had, which would further validate the diagnosis.

The timing after the service really helps confirm what you've found. To be specific about my codes: getting P0299 and P2563, which perfectly match the boost pressure and actuator valve issues you mentioned. After looking into repair options based on your feedback, I think I will proceed with the workshop visit. The 250 Euro cost seems very reasonable, especially considering the current fuel waste and performance issues. The fact that your repair has lasted 40000km without issues is particularly reassuring. My main concern was ending up with an expensive turbo system replacement, but it sounds like the actuator fault is the likely culprit. Will have them check those post-service connections too, makes perfect sense that disturbed fittings could contribute to these symptoms. Thanks for helping narrow down the problem. Will proceed with getting the turbo actuator checked and report back on whether my repair experience matches yours.