Audi A5 Diesel: Rough Running & Drift Comp Issues

I had a really similar issue with my 2018 Audi A4 diesel last winter. Having some experience with diesel engines, I recognized the symptoms immediately as fuel injection related. The onboard diagnostics showed similar error codes related to drift compensation adjustment. Initially, my mechanic connected the diagnostic system to analyze the fuel injection patterns and check the airflow sensors. Turns out one injector was faulty, causing uneven fuel distribution and rough running, especially during cold starts. The workshop replaced the defective injector and performed a complete fuel system calibration. Total cost was 515 Euro, covering parts, labor, and the essential compensation adjustment procedure. Since then, the engine has run smoothly with no check engine lights. Before suggesting specific fixes for your A5, could you share: Current mileage? Are you noticing any black smoke from exhaust? Does the rough running improve after the engine warms up? Any unusual fuel consumption changes? Have you had any recent fuel system maintenance? This information would help determine if your issue matches what I experienced with my A4.

Last service was at 152000km, currently at 155073km. The black smoke is minimal, but fuel consumption has increased about 15% over the past month. The rough running does improve once warm, which aligns with your A4 experience. The performance tuning parameters from my onboard diagnostics also show inconsistent readings compared to baseline. Your suggestion about checking the airflow sensors and injector patterns makes sense given the symptoms. The system reset alone probably wont fix the underlying problem. Will schedule a workshop visit for a full diagnostic scan and fuel system inspection based on your feedback.

Thanks for providing those details. Comparing this to my A4 experience, the symptoms are nearly identical. The 15% fuel economy decrease combined with rough cold running strongly suggests injector issues, just like I faced. The improved running after warmup is typical for injector-related problems, as the higher operating temperatures help compensate for irregular fuel delivery. My onboard diagnostics showed similar inconsistent performance tuning readings before the repair. Since we have such similar cases, I would specifically request the workshop to: 1. Test injector spray patterns 2. Perform a complete airflow sensors validation 3. Run a full system reset after repairs The fuel consumption increase you mentioned is actually slightly worse than what I experienced (mine was around 10%). This could indicate the problem has progressed further or multiple injectors might be affected. Given your mileage is similar to when my issue occurred, its worth having them inspect the entire fuel delivery system while they are at it. The investment in a thorough diagnosis saved me from recurring issues later. Would you mind updating the forum once you get the workshop results? It would help validate if these diesel injection issues are a common pattern at this mileage point.

Thanks for all the detailed responses and sharing your A4 experience. The correlation between our symptoms has been really helpful in narrowing down the likely cause. Based on the diagnostics and your repair experience, I will definitely have the workshop focus on the fuel injection system. The matching patterns of rough cold starts, increased fuel consumption, and drift compensation issues make a lot of sense now. I will request the complete diagnostic process you outlined, especially the injector spray pattern testing and airflow sensors validation. The fact that my fuel economy drop is more severe at 15% does concern me that this could be a multi-injector problem. Will update the forum after the workshop visit with the final diagnosis and repair details. The correlation between our vehicles mileage points and symptoms should provide useful data for other diesel owners facing similar fuel system issues.