Q3 Power Loss & Jerking: Lean Engine Mystery Revealed

I had almost the exact same issue with my 2019 Audi Q5. With some experience working on cars, I can share what happened in my case. The symptoms were identical, rough running, power loss, and check engine light. After taking it to the workshop, they diagnosed a faulty fuel injector. The diagnostic showed the engine was running lean, similar to your situation, causing the jerky acceleration. The repair involved: Testing all fuel injectors, Replacing one defective injector, Cleaning the throttle body while they were at it, Programming the new injector to work with the ECU Total cost was 515 Euro including parts and labor. The fix completely resolved the symptoms. The engine ran smooth again with normal power delivery. Before giving more specific advice, could you share: Current mileage on your Q3? Does the problem get worse when the engine is cold? Have you noticed any unusual fuel consumption? Are there any other warning lights besides the check engine light? Have you had regular maintenance done, including spark plugs? These details would help determine if your issue is similar to what I experienced with the injector or if it might be related to other components like the oxygen sensor or catalytic converter.

Thanks for sharing your experience. After reading about your similar symptoms, I looked closer at my maintenance records. My Q3 only has 30184 KM and had its last service 3 months ago. The rough running and power loss seem most noticeable when accelerating. I have noticed the fuel consumption has increased slightly. I checked the service report and the throttle body was actually cleaned during the last maintenance. The fuel injectors were not inspected though. Given the symptoms match your experience exactly, I will have the workshop focus on testing the fuel injectors and check the oxygen sensor readings. Do you remember if the diagnostic trouble codes in your case specifically pointed to the fuel injectors? I want to make sure I communicate the symptoms clearly when I take it in.

Thanks for those additional details. Yes, in my case the diagnostic trouble codes pointed to a fuel system issue, specifically showing lean conditions in one cylinder bank. The mass air flow sensor readings were normal, which helped narrow it down to the fuel injectors. Given your Q3 has similar symptoms and the throttle body was recently cleaned, I am even more convinced you are dealing with a fuel injector problem. The increased fuel consumption you mentioned is another typical sign, as the ECU tries to compensate for the lean condition by adding more fuel overall. When my injector was failing, I also noticed: The rough running was most pronounced between 2000-3000 RPM, The check engine light would occasionally flash during heavy acceleration, The power loss was inconsistent, sometimes better, sometimes worse The workshop confirmed the diagnosis by: 1. Checking fuel pressure at the rail 2. Running injector pulse tests 3. Measuring fuel trim values 4. Testing oxygen sensor response The repair solved all issues immediately. Just make sure they properly program any new injector to match your ECU specifications. The programming alone was about 95 Euro of my total repair cost. Given your lower mileage, this might even be covered under warranty, which I unfortunately missed by a few months on my Q5.

Thanks for all the feedback. Your experience helps a lot since the symptoms match perfectly. My car is still under warranty, so I will definitely mention these specific issues when I take it in. The jerking is most noticeable in that same RPM range you mentioned, between 2000-3000. The check engine light has been steady rather than flashing, but the power loss definitely comes and goes just like you described. I am now quite confident this likely involves the fuel injectors rather than the mass air flow sensor or intake manifold issues I initially suspected. I will specifically ask them to: Check fuel pressure, Test all injectors, Verify fuel trim values, Inspect oxygen sensor readings I will book an appointment tomorrow and have them focus on the fuel system. Since the throttle body was already cleaned during recent maintenance, we can rule that out. Will update once I get it diagnosed and repaired. Thanks again for helping me narrow down the likely cause before taking it to the workshop.