Audi A4 TFSI Power Loss Points to Sensor Issues

Having some experience with fuel system issues, I dealt with very similar symptoms on my Audi A5 2.0 TFSI (2017). The symptoms you describe match exactly what I experienced, inconsistent power delivery, rough running, and stalling issues. After diagnostic testing, it turned out to be a faulty fuel injector affecting the air-fuel ratio. The workshop connected their diagnostic tool which showed irregular fuel spray patterns. They also checked the oxygen sensor and mass airflow sensor readings, but these components were functioning correctly. The repair involved replacing the defective injector and performing a full system calibration. Total cost was 515 Euro, including parts and labor. The car has been running smoothly since then, with proper power delivery and no check engine light. To better assist, could you provide: Current mileage, Any recent maintenance history, Whether the check engine light is solid or flashing, If you notice any unusual fuel consumption, Any specific driving conditions when symptoms worsen These details would help determine if your issue is identical to what I experienced or if there might be other factors involved with your specific case.

Thanks for the reply. My mileage is 178064 KM and last service was done at 175000 KM. The check engine light stays solid, not flashing. Fuel consumption has increased by about 15% in the past month. Symptoms definitely get worse during cold starts and when the engine is under load, especially during highway merging. The throttle body was cleaned during the last service, but the fuel injection system hasnt been serviced since purchase. The rich mixture condition seems most noticeable when the engine is cold. This makes me think the oxygen sensor might not be reading correctly during warm-up phase. Would a faulty injector typically cause increased fuel consumption like this? And should I consider a full fuel system cleaning before replacing parts?

I can definitely add more insight based on my experience with the same issue on my A5. After that injector replacement I mentioned, I also noticed that fuel consumption remained slightly elevated even after the repair. This led to discovering that my catalytic converter had been damaged by the rich fuel mixture over time. The oxygen sensor readings were actually masking a bigger problem. While my initial injector fix helped, the complete solution required: 1. Full fuel injection system cleaning 2. Replacing one faulty fuel injector 3. Installing a new catalytic converter due to damage from rich running Total repairs came to 1850 Euro but solved all issues including: Normalized fuel consumption, Eliminated cold start roughness, Restored proper throttle response, Resolved check engine light Based on your symptoms, particularly the cold start issues and increased fuel consumption, I strongly recommend having the mass airflow sensor checked along with the oxygen sensor readings. These components work together to maintain proper fuel mixture, especially during warm-up. Your mileage also suggests its time for a comprehensive fuel system service. The throttle body cleaning was a good start, but the entire fuel injection system likely needs attention to prevent similar issues from recurring.

Thanks for the detailed information. The symptoms you described, combined with the high fuel consumption and cold start issues, really help explain what could be wrong. Based on your feedback about the catalytic converter damage you experienced, I will definitely have both the fuel injection system and catalytic converter checked. The connection between the rich fuel mixture and potential converter damage makes a lot of sense. Your repair sequence also matches the progression of my symptoms, starting with rough running and gradually developing into higher fuel consumption. I will request a full diagnostic scan focusing on the air-fuel ratio along with inspection of all sensors. The fact that the check engine light stays solid rather than flashing at least suggests no severe misfire is occurring. I will schedule a complete fuel system service first, then address any faulty components identified during testing. The total repair cost of 1850 Euro you mentioned helps set realistic expectations for what I might be facing if multiple parts need replacement. Let me know if you experienced any other symptoms I should watch for or have the workshop check while they diagnose the issue.