Audi TT Fuel System Failures: Fix It Right First Time

As someone with moderate experience working on similar issues, I dealt with almost identical symptoms on my 2006 Audi A4 2.0T. Your description matches the classic signs of fuel delivery problems, particularly the rough idle and reduced power output. In my case, after changing the fuel filter, the engine started showing these exact symptoms. The workshop connected their diagnostic tool and found that the fuel pressure sensor was giving incorrect readings, causing the fuel pump to operate inefficiently. The fix was relatively straightforward, they needed to clear the error codes and perform a proper calibration of the fuel pressure monitoring system. The whole procedure cost 45 Euro and resolved the engine misfire and rough idle issues completely. Before jumping to conclusions about the fuel pressure regulator, it would be helpful to know: Have you recently had any fuel system maintenance done? Are you getting any specific error codes? Does the rough idle happen more frequently when the engine is cold or warm? What is your current fuel efficiency like compared to normal? These details would help determine if your issue matches what I experienced or if it might be something else in the fuel delivery system.

Last service was at 141394km with a full engine check. The fuel rail pressure was inspected and showed signs of inconsistency. After running diagnostics, the fuel pressure sensor readings fluctuated between 2.8 and 3.2 bar at idle, which indicates a pressure drop issue. The engine misfire seems most noticeable after the engine warms up. My fuel consumption increased from 8.5L/100km to around 10.2L/100km over the past month. The error code reader shows P0087 (Fuel Rail/System Pressure Too Low) and occasionally P0191 (Fuel Rail Pressure Sensor Circuit Range/Performance). Will try cleaning the fuel system first before replacing components.

Thanks for providing those details, they actually align perfectly with what I experienced. The pressure readings you mentioned match the symptoms I had before fixing my A4. Those fluctuating pressure values between 2.8 and 3.2 bar are a clear sign of fuel system pressure problems. The P0087 code was exactly what my car threw before the repair. The fuel efficiency drop you noted from 8.5 to 10.2L/100km mirrors my situation, my fuel consumption also increased by about 20% when the issue started. While cleaning the fuel system is a good first step, in my case it only provided temporary relief. The real fix came when we replaced both the fuel pressure sensor and the fuel pressure regulator as they work together in maintaining proper fuel delivery. The rough idle completely disappeared after this repair. A telling detail is that your engine misfire gets worse when warm, this was the same for me and its typically a sign of a failing pressure regulator rather than just a dirty fuel system. The total repair on my A4 ended up costing around 380 Euro including parts and labor, but it completely resolved the power loss and rough idle issues. Given your identical symptoms and error codes, you might want to prepare for a similar repair path.

Based on your fuel pressure readings and error codes, the rough idle issues definitely seem linked to the fuel delivery system. The P0087 code plus the pressure fluctuations between 2.8-3.2 bar make sense given my fuel consumption increase. Will start with a thorough fuel system cleaning since its relatively inexpensive. But your experience suggests I should budget around 380 Euro for a potential fuel pressure regulator and sensor replacement if cleaning doesnt resolve the pressure drop problems. The similar symptoms, especially the worsening rough idle when warm and matching error codes, are convincing evidence that my TT likely needs the same fix your A4 did. At least now I can go into the repair with a clear idea of the costs and proper diagnostic path. Thanks for confirming the connection between the fuel rail pressure issues and my engine performance problems. Will update once I get it sorted.