RS3 Power Loss & High Fuel Use: Turbo System Alert

Had a very similar issue with my 2013 S3. After experiencing reduced engine performance and noticeable turbo lag, I took it to a workshop with some experience working on turbocharged engines. The main symptoms matched yours, poor acceleration, high fuel consumption, and inconsistent boost pressure. The diagnostic scan revealed issues with the pressure sensor readings. After checking the intake manifold and various connections, they identified a faulty vacuum switching valve affecting the turbo control. The repair involved: Complete diagnosis of the boost control system, Replacement of the vacuum switching valve, System pressure testing, Recalibration of boost settings Total cost was 140 Euro including parts and labor. Since the fix, turbo response is back to normal and fuel economy has improved significantly. The compressor surge issues disappeared completely. To help diagnose your case more accurately, could you share: Any specific error codes from the diagnostic scan? When did you first notice the performance drop? Does the turbo lag vary with engine temperature? Have you noticed any unusual sounds from the engine bay?

The issue was resolved after replacing both the boost controller and pressure sensor. At 152257KM, these parts were likely due for replacement anyway. After extensive testing, no intake manifold leaks were detected. The compressor surge symptoms disappeared immediately after the fix. The total repair cost was 380 Euro including: New boost controller unit, Pressure sensor replacement, System diagnostics, Calibration Performance is now back to factory specs and fuel consumption has normalized. No pressure drop issues since the repair. Would recommend checking these components first if anyone experiences similar symptoms. The engine pulls strong again through all RPM ranges and boost builds smoothly without the previous lag.

Thanks for the update on your RS3 repair. Your experience matches what I found with mine, those boost control components are often the culprit for these symptoms. My 2011 RS3 had nearly identical issues around 160000KM. The bypass valve was actually showing similar symptoms before I replaced my boost controller and sensors. I'd suggest anyone else with these symptoms to have their entire boost control system inspected, including the vacuum lines and boost solenoid connections. One thing I noticed after my repair that might be helpful, the intake manifold pressure readings were much more stable on the diagnostic readouts. Before the fix, they would fluctuate wildly under load. The workshop confirmed this is a common indicator of failing boost control components on these engines. Interesting that your repair cost was 380 Euro, I paid about 350 Euro for almost the same work. Good to know the pricing is fairly consistent for this type of repair.

Great news about solving those boost control issues. The diagnostic steps and repair costs you shared match what I experienced exactly. My final scan showed fault code P0234 related to overboost conditions, which cleared up right after replacing those components. First noticed the performance drop during highway merging, where the turbo lag was most obvious. Engine temperature didnt seem to affect the boost response issues. The compressor surge completely disappeared after the fix. No more pressure drop problems or excessive fuel consumption. The 380 Euro repair cost was totally worth it given how much better the car runs now. Boost builds smoothly and consistently through the rpm range. Interesting point about the system pressure readings, the new sensor shows much more stable values than before. For anyone dealing with similar symptoms, checking the boost solenoid and controller first could save time in diagnosing these kinds of turbo performance problems.