Audi Stalling After Fill-Up Points to Fuel System Issues

As someone with moderate experience working on Audis, I had a very similar issue with my 2013 Audi A3 last winter. The symptoms you describe match what I experienced, particularly the stalling at idle and check engine light. In my case, the fuel quality wasnt the culprit, though poor fuel can cause these symptoms. The actual problem was a faulty connection in the wiring harness leading to the fuel pump controller. The workshop performed a diagnostic scan which pointed to irregular fuel pump signals. After inspecting the wiring, they found a corroded plug connection that was causing intermittent fuel delivery issues. The repair involved cleaning the connector and replacing the damaged wiring section, costing 95 Euro including diagnostic time. Since the fix, the engine has run perfectly with no stalling or warning lights. Before jumping to conclusions about fuel contamination or needing fuel system cleaning, you should: 1. Get the error code read 2. Check if the problem occurs consistently or only after refueling 3. Monitor if the engine performance changes when the fuel tank level drops Could you share: Which engine variant your A4 has? Does the stalling happen immediately after starting or only when warm? Have you noticed any other symptoms like rough idle or hesitation during acceleration? This information would help determine if your issue matches what I experienced with the wiring problem or if it points to actual fuel system issues.

Service history: Last maintenance at 112583 KM, full service including spark plug replacement and throttle body cleaning. After testing with a quality fuel from a different station, the problem persists. The rough idle and stalling issues have actually gotten worse. I noticed the engine sound is a bit rougher now, especially during cold starts. The engine stumbles badly when pressing the gas pedal and occasionally the tachometer drops to zero at stoplights. I also noticed a slight fuel smell, which makes me worry about the fuel system having more serious problems than just contamination. Seems the fuel filter might be completely clogged, possibly from debris in the combustion chamber after the recent service. Will get it checked right away since these symptoms point to a restriction in the fuel delivery system.

Had similar escalating symptoms with my A3 after my feedback above. When the fuel filter got completely clogged, engine knock became very noticeable, especially during cold starts. The fuel smell you mention matches my experience too, turned out fuel wasnt flowing properly through the system. What started as a suspected wiring issue in my case actually revealed multiple problems. The clogged fuel filter was creating inconsistent fuel pressure, leading to poor fuel mixture and the symptoms you describe. The tachometer dropping suggests the engine is getting starved of fuel, just like mine did. After replacing the fuel filter and running fuel system cleaner through a fresh tank, the rough idle and stalling completely resolved. The total repair including parts and labor came to 280 Euro. I strongly recommend getting the fuel system checked as a priority. The combination of fuel smell, rough running, and stalling points to restricted fuel flow rather than an electrical issue as I initially thought with my car. The recent service could indeed have dislodged debris that is now blocking the filter. Have you noticed if the problems get worse after driving for a while? This could confirm if heat is making the fuel delivery issues more pronounced, which would align with a restricted fuel filter scenario.

Thanks for the update and clarification on the service history. I agree the symptoms are pointing to a fuel delivery problem. The fuel smell combined with stalling really suggests restricted flow, and I suspect the clogged fuel filter theory is spot on. The engine knock during cold starts is particularly concerning. Combined with the rough idle and stumbling when accelerating, these symptoms match classic signs of fuel contamination or severe fuel filter restriction. The fact that switching fuel stations didn't help rules out just bad fuel. The tachometer dropping to zero is exactly what happens with insufficient fuel delivery. When the fuel pressure drops too low, the engine essentially starves and stalls. This matches with the theory about debris getting into the combustion chamber and fuel system during the recent service. I will schedule an urgent appointment to have the fuel system diagnosed properly. They will need to: Replace the fuel filter, Check fuel pressure readings, Inspect the fuel lines for any other restrictions, Clean the fuel system if needed The symptoms have definitely gotten worse over time, and I don't want to risk damaging the engine by continuing to drive it in this condition. Better to fix it now before it leads to more expensive repairs.