Audi Q5 Diesel: Power Loss Points to Turbo Issues

I had a similar issue with my 2013 Audi Q7 diesel and can share my experience since I have some experience working on diesel engines. The symptoms match what I encountered, increased fuel consumption, power loss, and check engine light. Initially, my mechanic checked the fuel injectors and turbocharger, thinking those were the likely culprits. However, the root cause was actually traced back to carbon buildup that occurred due to a previous EGR valve issue that hadnt been properly addressed. The carbon deposits were affecting engine performance, but since it was linked to the prior EGR repair being done incorrectly, the cleanup work was covered under warranty. The workshop did a thorough carbon cleaning and properly fixed the EGR system. After the repair, fuel consumption returned to normal and power was fully restored. To better assist with your situation, could you share: Current mileage, Any recent repairs or maintenance, Whether you notice any engine knocking sounds, If the timing belt has been replaced according to schedule, What error codes your scanner is showing This information would help determine if your issue follows a similar pattern or might have a different cause.

Thanks for sharing your experience. My Q5 has 21828 KM and had its last service 3 months ago. The symptoms have gotten worse lately with noticeable engine knocking when accelerating. After reading your response, I checked with my repair records and found the EGR valve was indeed serviced last year. I am now concerned the carbon buildup could also be affecting my fuel injectors and turbocharger performance. The timing belt was replaced at the recommended interval. The error codes point to cylinder pressure issues, but I will have the carbon deposits checked first before proceeding with more extensive repairs. This could explain both the power loss and increased fuel consumption without requiring major component replacement. Would you recommend any specific fuel additives that helped with the carbon cleanup in your case?

Thanks for the additional details about your Q5. Based on the knocking sound and your car's symptoms, it sounds remarkably similar to what I experienced. Since both our cars had previous EGR work and are showing similar issues, the carbon buildup theory seems even more likely. After my repair, I learned that carbon deposits can significantly impact cylinder pressure, which explains the error codes you are seeing. In my case, fuel additives alone werent enough. The carbon buildup had affected multiple components including the intake manifold and was severe enough to require professional cleaning. The mechanic also found the head gasket was showing early signs of wear, likely from the increased pressure caused by the carbon deposits. The knocking during acceleration is particularly concerning as it could indicate the carbon deposits are affecting your piston rings or spark plug operation. I would strongly suggest having this checked soon to prevent more extensive engine damage. From my experience, the repair process involved: 1. Professional carbon cleaning 2. Inspection of fuel injectors 3. Testing cylinder pressure 4. Verifying EGR system operation This resolved both the performance issues and abnormal fuel consumption completely. The entire job took about 2 days but saved me from more expensive repairs down the line.

Thanks for the thorough follow-up. I better understand how serious the carbon buildup issue can be now, especially its impact on the fuel injectors and turbocharger performance. Given my mileage of 21828 KM and the recent EGR service, your experience really helps confirm my suspicions. The knocking during acceleration has definitely become more noticeable this week, and knowing it could be damaging my engine makes me want to address this quickly. I will skip trying fuel additives and schedule a professional cleaning right away. The fact that your repair involved a complete inspection of the intake manifold and fuel injection system makes sense, especially considering my error codes pointing to cylinder pressure problems. I just booked an appointment for next week to have them perform: Carbon deposit cleaning, Full inspection of the turbocharger, Fuel injector testing, Complete pressure test, EGR system verification Will update once I know what they find. Hopefully catching this early will prevent any major engine damage and restore normal performance without needing extensive repairs.