Audi S5 Fuel Rail Sensor Issues Killing Performance

Having some experience working on Audis, I ran into a very similar issue with my 2012 Audi S4. The symptoms were exactly as you describe, rough idle, power loss, and persistent check engine light related to the fuel rail pressure sensor signal. After checking the diagnostic codes, my workshop confirmed the fuel pressure sensor was sending incorrect signals to the engine control unit. This was causing the fuel injection system to malfunction, leading to those performance issues you mentioned. The total repair came to 240 Euro, which included replacing the defective pressure sensor and running a complete diagnostic check to ensure no other fuel system components were affected. Before you proceed with repairs, could you share: Current mileage on your S5, When was the last fuel system maintenance performed, Are there any other warning lights besides the check engine light, Have you noticed any fuel consumption changes This information would help determine if your issue is isolated to the sensor or if there might be related fuel system problems that need attention.

Thanks for the detailed feedback. My S5 has 148105 KM and just had its regular service 2 months ago. Definitely experiencing higher fuel consumption lately. The fuel rail pressure issues started showing up about 2 weeks after that service. Interestingly, no other warning lights have appeared, just the check engine light. Based on your experience, sounds like I should focus on the pressure sensor rather than assuming a complete fuel system overhaul is needed. The similar repair cost on your S4 gives me a good baseline for what to expect.

Thanks for providing those details. Based on your mileage and the timing of the issues, I'm even more convinced we're dealing with the same pressure sensor problem I had on my S4. The increased fuel consumption you're experiencing matches exactly what I noticed before getting the sensor replaced, my engine was compensating for incorrect pressure readings by adjusting the fuel mixture. After getting my pressure sensor replaced, the engine performance returned to normal within a few drive cycles. The stalling issues disappeared completely, and fuel economy improved significantly. One thing I learned during my repair, the sensor's lifespan often correlates with total engine cycles rather than just mileage, which explains why these issues commonly appear around the 140-150K mark. Since you mentioned the regular service was just 2 months ago, it might be worth checking if any fuel system work was done then that could have disturbed the sensor. In my case, the workshop also performed a fuel system cleaning as preventive maintenance after replacing the sensor, which cost an extra 85 Euro but helped ensure optimal performance. Have you noticed if the engine stalling gets worse when the engine is fully warmed up? This was a telling symptom in my situation that helped confirm it was indeed the pressure sensor and not a larger fuel system issue.

My car has been stalling more frequently when warm, especially after longer drives. Your experience really helps confirm my suspicions about the fuel rail pressure sensor being the culprit. Glad to hear replacing the sensor fixed your stalling and power issues without needing extensive fuel system repairs. Think I will schedule the repair and go for the fuel system cleaning too. The total cost around 325 Euro for both services sounds reasonable, especially if it resolves these engine performance problems. Based on the timing of my issues starting after the recent service, I will mention this to the shop when I bring it in. The check engine light and these symptoms have been stressing me out, but knowing your S4 had such similar fuel injection problems that were fixed with just a sensor replacement gives me confidence about the repair path forward. Will update once I get it sorted.

Audi s5 3.0 tfsi engine malfunction indicator lamp is on. Diagnosed with codes P0172, P0175, P0141, and P0140, these codes indicate insufficient air for proper combustion. I was reading on this site and it seems similar to a problem with the fuel pressure sensor. Also, when I give it full throttle, I see a lot of moisture coming from the exhaust. I initially thought of a mass air flow sensor, but this car doesn't have one. Then I thought, I hope it's not the supercharger. What could I do or try before going to a garage? Regards, Wesley

(Translated from Dutch)

Start by checking the air intake system for any leaks or blockages, as these can cause the engine to run rich, leading to the P0172 and P0175 codes. Inspect the air filter to ensure it's clean and properly installed. Also, examine the vacuum lines for any cracks or disconnections. If these checks don't resolve the issue, consider inspecting the oxygen sensors, as the P0141 and P0140 codes suggest potential issues there. If the problem persists, it might be best to have a professional mechanic take a closer look, especially given the moisture from the exhaust, which could indicate a more complex issue. Let me know how it goes or if you have further questions!

Thanks for the tip, I'll see if I can find something. I've also found an Audi expert, so I can always take my car there. I'll keep you updated.

(Translated from Dutch)

Check the air intake system and vacuum lines as a first step. If the issue persists, have the oxygen sensors inspected. Keep me updated on your progress or if you have more questions!