A3 Power Loss & Smoke Points to Faulty EGR Valve

I had a very similar issue with my 2017 A3. The symptoms you describe match exactly what I experienced, rough idle, power loss, and increased vehicle emissions. Being somewhat experienced with automotive repair, I initially tried cleaning the EGR valve myself, but the problem persisted. The workshop diagnosed a completely jammed EGR valve which was causing significant running issues. The repair process took about 4 hours total. They had to remove several components to access the valve, replace it with a new unit, and then run diagnostic tests to ensure proper function. Total cost was 355 Euro including parts and labor. After the repair, the rough idle completely disappeared and power delivery returned to normal. Most importantly, the car passed the emissions test without any issues. The vacuum leak symptoms and hissing noise were also resolved. To provide more specific advice about your situation, could you share: Current mileage on your A3? When did these symptoms first appear? Any recent maintenance or repairs? Any other warning lights besides check engine? Have you scanned for error codes? These details would help determine if your case is similar and if additional checks might be needed before proceeding with repairs.

Thanks for your helpful insights about the EGR valve issue. My A3 is currently at 15793 KM and just had its annual service last month. No other warning lights besides the check engine light, and symptoms started about 2 weeks ago. I ran a diagnostic scan which showed error code P0401 indicating insufficient EGR flow. Given all symptoms match, I will proceed with the repair. The workshop quoted 425 Euro for the complete job.

Thanks for providing those details. Based on the error code P0401 and your low mileage, this definitely confirms my initial suspicion about the EGR valve. The price quoted for your A3 is reasonable considering the parts cost more than on my A3. Since my repair, I have had zero issues with rough idle or power delivery. One tip though, make sure they check the catalytic converter during the repair. In my case, the faulty EGR valve had caused some carbon buildup that partially restricted the cat. The workshop cleaned this as part of the service which helped restore full performance. The timing of your symptoms matches the typical failure pattern, these valves can get stuck due to carbon deposits even with regular maintenance. The good news is that fixing it now will prevent any issues with your next emissions test and should immediately resolve the power loss and rough running. From my experience, request they also inspect the intake manifold while they have everything apart. This preventive check costs nothing extra but can catch potential related issues early. The excessive vehicle emissions you are experiencing now should clear up completely after the repair.

Thanks for the detailed feedback, especially about checking the catalytic converter. I have booked the car in for next week and specifically asked them to inspect both the intake manifold and cat while doing the EGR valve replacement. The error code P0401 combined with all these symptoms seems pretty conclusive. Really hoping this fixes the power delivery issues and rough idle, the car has been almost undriveable lately. The 425 Euro quote sounds fair based on your experience, though I will ask them about any additional costs if they find issues with the catalytic converter. Good to know this should sort out the vehicle emissions before my next test.