RS6 Fuel Pressure Issues, Regulator Problem?

During routine maintenance on my 2006 S6, I encountered similar symptoms with unstable fuel pressure readings. I have some experience working on these engines and recognized the classic signs of pressure drop issues. After changing the fuel filter, the check engine light came on and the engine started showing rough idle symptoms. The fuel system was giving erratic pressure readings through the sensor. Initially suspected the pressure regulator, but it turned out the fuel pressure sensor needed recalibration after the filter change. Took it to a workshop where they performed a diagnostic reset and sensor calibration. Total cost was 45 Euro for the diagnostic work. The fuel pump and remaining fuel system components were all functioning normally, it was purely a sensor calibration issue triggered by the filter replacement. To better assist with your RS6 issue: Have you recently done any fuel system maintenance? What are the specific error codes showing? Is the rough idle constant or does it come and go? Does the power loss happen gradually or suddenly? These details would help determine if your situation matches what I experienced or if you might be dealing with a different underlying issue.

After 24785KM and my last service being 2 months ago, I can confirm the check engine light appeared suddenly without any recent maintenance work. The rough idle is constant and power loss happened gradually over 2-3 days. The error codes show P0193 and P0087, which align with fuel pressure sensor circuit high input and fuel rail pressure too low. The fuel efficiency has dropped significantly, suggesting this could indeed be more than just a sensor issue. When driving, the engine responds poorly to throttle input, especially above 3000 RPM. The fuel pump makes a slightly louder noise than usual during cold starts. Looking forward to additional insight based on these details.

Those error codes combined with the gradual power loss and constant rough idle actually match what I experienced before I discovered the sensor calibration issue. However, given your description of the fuel pump noise and poor throttle response, I suspect your case might be more serious than mine was. On my S6, I eventually discovered the problem was a combination of a failing fuel pressure sensor and a partially clogged fuel filter, causing engine misfire symptoms above 3000 RPM. The loud fuel pump noise during cold starts was actually the pump working harder to compensate for the pressure drop in the system. The significantly reduced fuel efficiency you mentioned is particularly concerning, as this suggests actual fuel delivery issues rather than just sensor problems. In my case, replacing both the pressure sensor and fuel filter resolved the problems completely. Total repair cost was around 380 Euro including parts and labor. Consider having the fuel pressure tested with an external gauge to verify if the readings match the ECU data. This will help determine if you are dealing with an actual pressure regulation issue or a faulty sensor reporting incorrect values. Based on my experience with these engines, testing the actual fuel pressure is crucial before replacing the regulator.

Thanks for the detailed response. You make a good point about verifying the actual fuel pressure against the ECU readings. I'll get an external pressure test done before proceeding with any parts replacement. The symptoms you described with your S6 sound very similar, especially the connection between the fuel pump noise and pressure compensation. The distinct similarity in error codes is also telling. I'll start by having them check both the sensor and filter since that combination worked in your case. My only hesitation about it being just the sensor and filter is that the engine misfire seems more severe, it's happening even at lower RPMs unlike your experience where it mainly showed up above 3000 RPM. The fuel efficiency drop is also quite dramatic, worse than what you described. I'll book it in for diagnostics tomorrow and make sure they do a complete fuel pressure analysis. Will update once I know more about the actual pressure readings versus what the sensors are reporting. The 380 Euro repair cost you mentioned seems reasonable if it solves these issues.

Hello, I have a small question. I have a 2013 RS6 C7 4.0 with a Stage 2 tune. The car runs perfectly when it's full. Once I get to 100-80km of range, I start to have misfires, unstable idling, until the engine cuts out. Then I restart it, it starts and cuts out immediately. (High fuel consumption, smell of gasoline, etc.) ⚠️ It does all this, but once I put in gas and have an average range of more than 120km, it doesn't do any of that; the engine runs fine and no longer stalls. Engine warning light sometimes on, Fault codes with ODIS: 0001 - Engine electronics 16497 P017200 Bank 1, fuel metering system, System too rich (11101101 active/static) 0001 - Engine electronics 16516 P017200 Bank 1, fuel metering system, System too rich (11101101 active/static) 0001 - Engine electronics 16475 P017500 Bank 2, fuel metering system, System too rich (11101101 active/static) 0001 - Engine electronics 16501 P017500 Bank 2, fuel metering system, System too rich (11101101 active/static) Also, I checked the low-pressure pump (fuel pump) pressure. When the engine runs well, it's on average 580-600, once the engine starts to misfire or cut out, the pressure drops to 200-250! For me, the low-pressure pump (fuel pump) is probably faulty, but I'd like to get an opinion before doing anything. -I would like to specify that the coils are in good condition; I have already replaced 3 coils, the others are in good condition. -The spark plugs have also been changed. Maybe the original pump is not enough since it has a Stage 2 tune and doesn't provide enough pressure or gives too much pressure when it gets low on fuel?

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It sounds like your low-pressure fuel pump might indeed be struggling to maintain adequate pressure, especially given the drop to 200-250 when the engine misfires or cuts out. This could be exacerbated by the Stage 2 tune, which demands more from the fuel system. Since the issue resolves when the tank is fuller, it might indicate that the pump is having difficulty drawing fuel when the level is lower, possibly due to a weak pump or a problem with the fuel pickup. I recommend checking the fuel pump and its connections for any signs of wear or damage. Consider upgrading to a high-performance fuel pump that can handle the increased demands of your tuned engine. Let me know how the inspection goes or if you have further questions!