Audi Q3 Stalls: Start-Stop System Malfunction Alert

I had a similar issue with my Audi Q5 2014, which has comparable electronics and engine start systems. With some experience working on Audi vehicles, I can share what happened in my case. The symptoms matched exactly, unusual shutdowns and irregular automatic restart behavior. Initially thought it was the idle stop system acting up, but it turned out the battery was actually failing despite appearing fine in basic tests. The workshop performed a complete diagnostic and found the battery was unable to maintain proper voltage under load, affecting the eco mode and start-stop functionality. Even though basic battery tests showed ok, the advanced testing revealed significant cell degradation. The fix included: New AGM battery installation, ECU recalibration for the starter motor system, Reset of the engine start control module Total cost was 290 Euro for parts and labor. Since the repair, no more unexpected shutdowns or start-stop issues. To provide more specific advice for your Q3: What engine size do you have? Are there specific error codes showing? Does the issue happen more frequently when using electrical accessories? How old is your current battery? These details would help determine if your issue matches what I experienced.

Latest service was at 112000 KM. Thanks for sharing the repair experience with electrical issues. My engine is a 2.0L TFSI. The error codes are P0087 and P0299, suggesting potential fuel pressure and turbo problems alongside the battery concerns. The stalling happens more with AC running, which makes me think it could be load-related like your case. The current battery is about 4 years old. The engine stalling occurs most frequently during slow traffic when the start-stop system should engage. Will probably need that advanced battery test you mentioned to rule out a failing car battery before looking at other components.

Based on those error codes and symptoms, your situation seems more complex than my initial battery-only issue. The P0087 (low fuel pressure) and P0299 (turbo underboost) codes, combined with the increased stalling when AC is running, point to multiple potential problems. While my case was resolved with just the battery replacement and system resets, your engine stalling is likely caused by a combination of: A weakening car battery affecting the idle stop system, Possible fuel delivery issues, Turbocharger performance problems The automatic restart system is particularly sensitive to battery condition. My starter motor also showed irregular behavior before replacement, similar to what youre describing in slow traffic. Recommend this testing sequence: 1. Advanced battery load test 2. Fuel pressure testing 3. Turbo boost pressure check 4. Full diagnostic on the start-stop system My repair ended up being simple, but your error codes suggest you should prepare for additional components needing attention. The 4-year-old battery is definitely at the age where it could be contributing to the engine stalling issues, just like in my case. Total repair costs could range 500-1200 Euro depending on which components need replacement. The key is proper diagnosis before replacing parts.

Thanks for the detailed follow-up information. The stalling with AC running definitely matches similar battery issue patterns others have experienced. Getting that advanced battery test makes sense as the first step, especially since my current battery is reaching the typical 4-5 year lifespan. Will have the workshop check the fuel pressure and turbo problems indicated by those error codes too. The starter motor behavior you described in slow traffic sounds identical to what I am experiencing. Your repair path gives me a good starting point to discuss with the mechanics. The 500-1200 Euro cost range helps set realistic expectations, though hoping its just battery-related like your case rather than deeper engine start or turbo issues. Will book the car in next week for diagnostics, focusing first on battery health and the fuel system before investigating turbo problems. The engine stalling is getting more frequent in traffic, so better to address it now before it becomes a bigger safety concern.