RS4 V8 Engine Stalling & Power Loss Needs Urgent Fix

Had similar symptoms on a 2012 S4 last month. The check engine light started flashing after fuel filter replacement, indicating a severe fuel system issue that required immediate attention. The symptoms matched yours, rough idle, power loss, and occasional stalling. Initial diagnosis pointed to the fuel pressure regulator, but after testing the fuel rail pressure showed the real problem was a failing fuel pump causing irregular pressure drop. This is a serious issue that can damage the engine if left unchecked. The fuel system needs proper diagnostic testing with specialized equipment to check pressure readings across different load conditions. The fuel pump replacement required dropping the tank and replacing several connected components to ensure proper system function. Important note: If the check engine light is flashing, avoid driving the car as this indicates potential catalytic converter damage. The V8 engine in these models is sensitive to fuel delivery issues, and running it with incorrect fuel pressure can lead to more expensive repairs. The repair restored normal idle, eliminated stalling, and brought back full power. These symptoms should not be ignored as they typically worsen and can lead to complete system failure.

Appreciate the detailed response about the fuel system issues. My symptoms do sound identical to what you experienced with that flashing check engine light and rough running. Really considering having it checked this week since engine misfires seem to be getting more frequent. Quick question, do you remember roughly what the final repair cost was? Also wondering if you had any other issues pop up since the fuel pump replacement? Want to make sure I budget properly for all potential fixes since the pressure sensor and related components might need attention too.

Got good news to share after getting the issue resolved. Unlike my initial fuel pump diagnosis, it turned out the fuel pressure regulator was actually the culprit, just as you suspected. After replacing it, the engine misfires completely stopped and the rough idle smoothed out. The repair was far less expensive than a full fuel pump replacement, total came to 45 Euro for fixing the error entry after the fuel filter change. The flashing check engine light hasnt returned in the past few weeks, and fuel efficiency is back to normal levels. The V8 is running perfectly now with proper fuel pressure restored. No other issues have emerged since the fix. If your symptoms match what I experienced, definitely get it checked soon to prevent any additional fuel system problems from developing. Important maintenance tip: make sure to also have them check the fuel filter since a clogged one can cause similar symptoms and put extra stress on the new regulator.

Finally got the car checked out and you were spot on with the diagnosis. Took it to a different shop this time, one specializing in performance vehicles. The fuel pressure regulator was indeed failing, causing those misfires and the flashing check engine light. Total repair came to 850 Euro including parts and labor. They also found the fuel rail needed cleaning and replaced a worn pressure sensor while they were in there. More than I wanted to spend but worth every cent, car runs like new again. The rough idle is completely gone and power delivery is smooth. No more stalling issues either. They did a full system pressure test afterward to confirm everything was working properly. Really glad I didnt wait longer as they mentioned the irregular fuel pressure was starting to affect other components. Thanks for helping point me in the right direction with this. Going to stick with this shop for future maintenance since they actually took time to properly diagnose the fuel system issues rather than just guessing.