Audi Q3 Stalling: Fuel Pressure Regulator Issues

Similar issues occurred on my Audi A4 2.0 TFSI from 2014. Having some experience with fuel system repairs, I initially thought it was the fuel pump when the engine misfire symptoms started. After changing the fuel filter myself, I encountered a pressure drop in the fuel rail that triggered similar symptoms, rough idle, stalling, and reduced power. The check engine light also came on. The workshop diagnosed it as an initialization error after the filter change, requiring a system reset and fuel pressure regulation adjustment. The total repair cost was 45 Euro, mainly for diagnostic time and electronic adaptation. The fuel efficiency returned to normal after the fix. Before suggesting specific solutions, could you share: Current fuel consumption compared to normal? Does the problem get worse after refueling? Have you recently had any fuel system work done? What error codes is the check engine light showing? These details would help determine if your issue matches what I experienced or points to a different fuel delivery problem.

Thanks for sharing your experience. Last service was at 74000 KM and the fuel consumption has increased from 7.8L/100km to around 9.5L/100km. The rough idle and engine misfire symptoms definitely get worse after refueling. The error code reader shows P0171 which suggests a lean fuel mixture. I checked the fuel pressure at the fuel rail using a gauge and noticed inconsistent readings at idle, fluctuating between 2.8-3.5 bar when it should maintain steady pressure. This seems to confirm the fuel regulator might be failing. Will likely have it checked professionally since the symptoms match what others described with faulty regulators.

Thanks for those details. The P0171 code and pressure fluctuations at the fuel rail definitely align with what I experienced, though my issue turned out more complex than initially suspected. After getting similar pressure readings on my A4, I had the fuel pressure regulator replaced, but the engine misfire and rough idle persisted. It turned out the fuel rail itself had developed hairline cracks causing pressure inconsistency. The entire fuel rail assembly needed replacement, which resolved both the lean condition and erratic fuel pressure. The increased fuel consumption you mentioned matches exactly what happened with my car, mine jumped from 7.5L/100km to around 9.3L/100km before the repair. The fluctuating pressure readings at idle are particularly telling, as a properly functioning fuel system should maintain steady pressure. Given your pressure test results and the similar fuel efficiency drop, I would recommend having both the fuel pressure regulator and the fuel rail inspected. In my case, focusing solely on the regulator would have missed the root cause. Worth noting that cleaning the mass airflow sensor might also help, as a dirty MAF can contribute to lean conditions and rough idle problems while masking underlying fuel delivery issues.

Based on all that helpful information, I believe I should move forward with a professional diagnosis focusing on both the fuel pressure regulator and fuel rail. The matching symptoms, especially the pressure fluctuations and increased fuel consumption, are too similar to ignore. My rough idle issues also seem consistent with what you experienced, particularly how the problems worsen after refueling. The P0171 lean condition code combined with the erratic fuel rail pressure readings really does suggest a fuel delivery problem beyond just the regulator. I will have the shop check the entire fuel system, including inspecting the fuel rail for potential cracks, since focusing only on the regulator might miss the actual cause. I will also ask them to clean the MAF sensor while they are at it. Will book an appointment this week and report back on what they find. The detailed pressure readings I took should help speed up their diagnostic process. Thanks for sharing your experience, it helped confirm I am looking in the right direction with the fuel delivery system.