A3 TDI Boost & Stalling: Likely Turbo System Failure

Had the same symptoms on my A4 2.0 TDI from 2015. The wastegate was stuck partially open, causing boost control issues and similar performance problems. The check engine light came on because the MAP sensor was detecting inconsistent pressure readings. The root cause was a defective wastegate actuator and accumulated carbon deposits. The repair involved: Complete wastegate replacement, Cleaning the turbo assembly, Installing new pressure sensors, Recalibrating the ECU This was a serious issue requiring immediate attention, as continued driving could have damaged the turbocharger. The repair took two full days at the shop. The symptoms you describe, especially the whistling sound and increased fuel consumption, strongly suggest wastegate problems rather than intercooler issues. Would recommend getting it diagnosed with proper diagnostic equipment to confirm the pressure readings. If left unrepaired, these boost control problems typically lead to further engine damage and potentially complete turbo failure. The stalling at idle is particularly concerning, as it indicates the engine is getting incorrect air-fuel mixture due to the faulty boost control system.

Thanks for sharing your experience. This sounds exactly like what I am dealing with on my Audi. The sluggish performance and especially the stalling at idle is driving me crazy. The pressure sensor readings and boost pressure issues you mentioned make a lot of sense, especially since my throttle body response feels very inconsistent. Did you notice if your turbocharger performance improved significantly after the repair? Also, would you mind sharing what the total repair cost was? Just want to get an idea of what to expect when I take it to the shop. Also, has everything been running smoothly since the fix or have you had any other related issues pop up?

Good news, since getting the repair done, the boost control system has been working perfectly. The turbo lag completely disappeared and throttle response is back to normal. The wastegate valve replacement fixed all the issues, including the annoying stalling at idle. Total repair cost was 860 Euro which included the new wastegate, labor, and recalibration. While not cheap, it was worth preventing more expensive turbocharger damage down the line. The intercooler and other components checked out fine once the faulty wastegate was replaced. Its been 6 months since the fix and everything is running smoothly. No check engine lights or boost pressure problems have returned. Fuel consumption is back to normal levels and the engine performs like it should. Getting it fixed promptly was definitely the right call before the turbo system sustained any permanent damage.

Based on the helpful advice, I took my A3 to a new mechanic who specializes in turbo systems. After running diagnostics, they confirmed it was indeed a faulty wastegate causing the boost pressure issues. The repair took about 2 days and cost 920 Euro total, which included replacing the wastegate, cleaning the turbo assembly, and recalibrating the ECU. The difference is incredible, no more turbo lag or whistling sounds. The check engine light is gone and the idle is perfectly stable now. Fuel consumption has returned to normal and the engine feels responsive again. The MAP sensor readings are all within spec according to the mechanic. Very glad I caught this before it caused damage to the turbocharger. The new shop did excellent work and I will definitely use them again for future repairs. Thanks for helping me diagnose the issue correctly.