Audi A5 Engine Stalls Due to Suspected Fuel Issues

Had a similar issue on my 2019 Audi A4 2.0 TFSI. Having some experience with fuel system problems, I recognized the symptoms you describe, engine stalling and knocking does point toward potential fuel contamination or connection issues. Took it to the workshop where they diagnosed a loose connection at the fuel pressure sensor. The plug had worked itself free over time, causing irregular fuel delivery. Total repair cost was 95 Euro for diagnostic and fixing the cable connection. Before assuming fuel contamination though, getting those error codes read is crucial. If it truly is wrong fuel or poor fuel quality, you might need a complete fuel system flush, which would cost significantly more than my repair. To help diagnose this better: When exactly did the stalling start after refueling? Does the engine run rough only at idle or also while driving? Have you noticed any decrease in fuel economy? Are you still using the same fuel station? What octane rating fuel do you normally use? Let us know these details so we can provide more targeted advice for your specific situation.

Thanks for the feedback. In my case (77350 KM, last service 2 months ago), I noticed the stalling started about 10 minutes after leaving the fuel station. The engine knock is most noticeable at idle, but the engine runs somewhat rough even while driving. Fuel economy has dropped by about 15%. The combustion chamber issues seem consistent with fuel contamination, I switched to a different station since then. I typically use 98 octane as recommended. I will get the error codes read tomorrow and update. Just added some fuel additives as a temporary measure, but not expecting miracles before properly diagnosing the root cause.

Thanks for those additional details. The symptoms match almost exactly what I experienced on my A4 before discovering it was more than just a sensor connection in my case. After that initial diagnosis I mentioned, the problems persisted and it turned out I actually had contaminated fuel from a station that had just received a fresh delivery. The fuel filter was completely clogged, causing inconsistent fuel pressure and that nasty engine knock you described. The full fix included: New fuel filter replacement, Complete fuel system flush, Fuel injector cleaning, Fresh fuel fill Total repair came to 780 Euro, but it solved all issues. The fuel economy returned to normal and the engine knock disappeared completely. Your 15% drop in fuel economy combined with the timing of symptoms strongly suggests fuel contamination rather than just a sensor issue like I initially had. The 98 octane you are using is correct, so that rules out wrong fuel grade. Those fuel additives might help temporarily, but based on my experience, I would prepare for a proper fuel system service. Getting those error codes will confirm, but the symptoms are textbook fuel contamination indicators.

The timing aligns with what I initially suspected. Thanks for sharing your experience, especially the details about your A4 case turning out to be contaminated fuel. Those repair costs give me a realistic picture of what I might be facing. I checked my fuel consumption numbers again and noticed the economy dropped closer to 20% now. The engine knock has gotten slightly worse over the last day, even with the fuel additives I added. Not taking any chances, booked the car in for tomorrow morning to get those error codes read and likely the full fuel system service. Will definitely need that fuel filter replacement and system flush by the sound of it. If it comes to 780 Euro like in your case, that would be worth it to prevent any long-term damage to the fuel injection system. The fuel quality issue caught me off guard since I always use high-octane fuel, but these things happen. Will post the diagnostic results and final fix once I get them. At least I know what to expect now based on the similar symptoms you described.