RS4 Rough Idle and Stalling Points to Fuel Sensor Issue

I went through something very similar with my 2021 RS5 last year. I have some experience working on cars but mainly stick to basic maintenance. The symptoms you describe match exactly what I experienced, rough idle, jerking during acceleration, and constant check engine light. Initially I also suspected the fuel pressure sensor, but it turned out to be a loose connector at the wiring harness near the fuel pump. The workshop diagnosed it quickly, finding that moisture had caused minor corrosion at the connection point, affecting fuel delivery and causing the engine misfire. They cleaned the connector, applied dielectric grease, and properly reseated it. Total cost was 95 Euro including diagnostic time. The actual repair took under an hour. Before suggesting more specific advice, could you share: Have you scanned for error codes? Does the engine misfire happen more when the engine is cold or warm? Did these issues start suddenly or develop gradually? Any recent work done on the fuel system? This information would help determine if your issue is identical to what I experienced or potentially something else in the fuel delivery system.

Thanks for everyone sharing their feedback. Just had my service done at 111884 KM and the mechanic found the root cause. The rough idle was related to a faulty fuel pressure sensor which also impacted the fuel delivery system. They replaced the sensor and cleaned the entire fuel system. Car runs perfectly smooth now with no jerking during acceleration. Total repair cost was 450 Euro including parts and labor. The fuel economy has also improved noticeably since the fix.

Thanks for the update on your RS4 repair. Your experience confirms my initial suspicion about the fuel pressure sensor being the culprit. The symptoms matched perfectly with my RS5 issue, though mine had a simpler fix with the loose connector. Great that they did a full fuel system cleaning along with the sensor replacement. That comprehensive approach likely explains why your fuel economy improved, clean injectors and optimal fuel delivery pressure make a big difference. The 450 Euro total seems reasonable for the parts and work involved. Just a heads up based on my experience, after this type of repair, its worth keeping an eye on the idle behavior for the next few weeks. Sometimes the engine control unit takes a bit of time to fully adapt to the new sensor readings. If you notice any slight rough idle, its usually temporary while the system calibrates. For preventive maintenance, I recommend using high-quality fuel and keeping the tank above quarter full, which helps maintain consistent fuel delivery and reduces stress on the fuel system components.

Thanks for the input. Just got back from the shop after having my 2023 RS4 serviced at 111884 KM, and they found the root cause. The rough idle and engine stalling were indeed caused by a faulty fuel pressure sensor that was affecting the entire fuel system. The shop replaced the sensor and did a complete fuel system cleaning. The check engine light is now off and the car runs perfectly smooth with no jerking during acceleration. Total repair cost came to 450 Euro including parts and labor. As a bonus, the fuel economy has improved significantly since the fix. Really glad to have this sorted out and appreciate the helpful suggestions from everyone who replied.