Wrong Fuel Suspected in Audi A3 Stalling Issues

I faced a similar issue with my Audi A4 2.0 TFSI from 2019. With some experience working on TFSI engines, I recognized these symptoms immediately. After refueling, my engine also showed unstable idle and check engine warnings. Initially suspected wrong fuel or poor fuel quality, but the workshop diagnosed a faulty fuel pressure sensor connection. The plug connection had worked loose, causing irregular readings in the fuel system. The fix was straightforward, they cleaned the connector, secured it properly, and cleared the error codes. Total cost was 95 Euro including diagnostic time. The fuel filter and rest of the fuel system were checked but found to be clean, ruling out contamination in the combustion chamber. To help diagnose your case more accurately, could you share: Build year of your A3, Exact error codes showing, Does it run rough only at idle or also while driving, When was your last fuel filter change, Which fuel grade you typically use These details would help determine if your issue matches what I experienced or points to actual fuel contamination.

Thanks for sharing. I am hitting 150412 KM and recognized similar symptoms in my A3. However, in my case engine knock started before the check engine light came on. The fuel system was thoroughly inspected and we found that water had contaminated the tank, likely from a problematic fuel station. The fix involved draining the entire fuel system, replacing the fuel filter, and running a fuel system cleaner through a fresh tank of high-octane fuel. The combustion chamber needed thorough cleaning to prevent long-term damage. Workshop managed to sort everything within a day, total repair cost was 450 Euro. Would suggest checking your fuel receipt, sometimes wrong fuel issues can be traced back to the specific fill-up that caused problems. Do you notice any metallic sounds when accelerating?

Thanks for the update on your A3 issue. On my A4, I never experienced engine knock before the warning lights, which definitely points to our problems being different. This matches with your water contamination finding versus my loose sensor connection. The metallic sounds you mentioned are classic signs of fuel problems affecting the combustion chamber. Water in the fuel system can cause serious engine knock by disrupting the proper fuel mixture. Your repair approach with system drainage and cleaning was more comprehensive than what I needed. Had similar high-octane fuel system cleaners recommended for my TFSI when they checked for contamination. Good practice even with clean fuel to maintain optimal combustion chamber conditions. My fuel filter was actually due for replacement anyway, so had that done preventively while they were checking the system. Since fixing the sensor connection, no engine knock or stalling issues have returned. Regular fuel quality from established stations seems key to preventing these problems. The TFSI engines are quite sensitive to fuel mixture variations.

I really appreciate all the insights. After my experience with water contamination and engine knock, I now carefully document each fill-up and stick to reliable stations. The fuel economy actually improved after the thorough fuel system cleaning, suggesting the contamination had been affecting performance for a while. The combustion chamber cleaning made a noticeable difference. No more metallic sounds or engine knock, and the idle is perfectly stable now. Interesting how similar symptoms led to different root causes between our cases, your loose sensor versus my contaminated fuel system. My workshop mentioned they see quite a few wrong fuel and contamination cases with TFSI engines. The 450 Euro repair cost was worth it to prevent more serious engine damage. Will definitely keep monitoring for any fuel system related symptoms and maintain strict fuel quality standards going forward. Good reminder about the fuel filter maintenance schedule too. Adding that to my regular service checks should help catch any future fuel quality issues early.