Audi Q5: Stalling and Rough Idle Points to Fuel Issues

I had very similar symptoms with my 2016 Audi Q3 2.0T last year. Having some experience working on VAG engines, I first suspected fuel system issues like you mentioned. The rough idle and jerking during acceleration were nearly identical to what you describe. After taking it to my regular workshop, they diagnosed a loose connection at the fuel pressure sensor plug. The connection had worked itself loose over time, causing inconsistent readings and making the engine management system adjust fuel delivery incorrectly. The fix involved cleaning the connector, securing it properly, and clearing the error codes. Total cost was 95 Euro for diagnostic and repair work. Pretty straightforward fix, though the symptoms can be quite concerning when they first appear. Before suggesting more specific solutions, could you share: Current mileage on your Q5? Any recent work done on the fuel system? Are there any specific error codes showing? Does the rough idle happen more when the engine is cold or warm? These details would help determine if your issue matches what I experienced with the sensor connection or if it might be something else in the fuel system like injectors or the fuel pump.

Latest service was done at 132000 KM, about 2 months ago. The fuel system had a pressure regulator replaced during that service. The error codes showing are P0171 and P0087. The rough idle happens consistently whether the engine is cold or warm. I notice the check engine light flickers occasionally during hard acceleration, which seems to align with the jerking sensation mentioned earlier. When the engine stalls, it always restarts immediately, though the rough idle continues.

Thanks for those details. Those specific error codes combined with the symptoms make me think your issue might be different from my loose connector problem, especially since you recently had the pressure regulator replaced. P0171 indicates a lean fuel mixture and P0087 points to low fuel rail pressure, this combination suggests we might be looking at either a failing fuel pump or a clogged fuel filter. In my Q3, when the fuel pump started failing about 6 months after my connector issue, it showed identical codes and symptoms. The consistent rough idle regardless of engine temperature, combined with the flickering check engine light during acceleration, strongly suggests fuel delivery problems rather than just a sensor issue. The immediate restart after stalling was also something I experienced with my failing fuel pump. Given that the pressure regulator was recently replaced, I would focus on: 1. Fuel pump, most likely culprit based on my experience 2. Fuel filter, if it hasnt been changed during recent service 3. A possible vacuum leak causing the lean condition When my fuel pump was replaced, the total repair cost was around 850 Euro including parts and labor. The repair completely resolved the engine misfire and rough idle issues. Do you notice any decrease in fuel economy compared to normal? This could help confirm if were on the right track with the fuel pump diagnosis.

I really appreciate all the detailed feedback. After reading about the similar issues with your Q3, and knowing these error codes seem to match a fuel pump problem, I think I'll have it checked professionally. Your experience with the fuel pump repair cost of around 850 Euro helps set my expectations. The fuel economy actually has dropped noticeably over the past few weeks, getting about 15% worse mileage than usual. This, combined with the rough idle, stalling issues, and error codes you mentioned, makes me more confident its likely the fuel pump as you suggested. I'll have them check the fuel filter too since its relatively inexpensive and could be contributing to the problem. The vacuum leak possibility is also worth investigating given the lean condition code. Before booking it in, I might double-check the recent service records to confirm if the fuel filter was changed during the pressure regulator replacement. Thanks for helping narrow down the likely causes, this will make the conversation with the repair shop much more productive.