Audi S8: MAP Sensor Issue Causing Power Loss & High Fuel Use

I dealt with nearly identical symptoms on my 2004 Audi S6 last year. Having some experience with sensor diagnostics, I first noticed similar performance issues, poor acceleration and higher fuel consumption. The root cause turned out to be a large vacuum leak affecting the intake manifold and MAP sensor readings. The pressure sensor was giving incorrect readings due to the leak, causing the engine management system to run rich. The repair involved: Full diagnostic scan, Smoke test to locate the vacuum leak, MAP sensor replacement, Intake manifold gasket replacement Total cost was 235 Euro including parts and labor. The shop completed everything in about 4 hours. For your S8, I would recommend getting the following checked: MAP sensor voltage readings, Intake manifold pressure readings, Vacuum system integrity Could you share: Current mileage? Any recent repairs or maintenance? Other warning lights besides check engine? Any unusual sounds, especially near the intake area? This information would help determine if your issue matches what I experienced with my S6.

My mileage is 51722 KM and last service was about 3 months ago. Thanks for the detailed response. I am hearing a slight whistling noise from the engine bay, and the car occasionally shows a brief EPC light alongside the check engine light. The sensor replacement cost you mentioned sounds reasonable. Did you notice immediate engine performance improvements after the repair? Also wondering if you had to do any ECU relearning after the manifold sensor swap. No other repairs recently except routine oil change and brake pad replacement during the last service. The car ran perfectly fine until these symptoms started appearing about 2 weeks ago.

Thanks for the additional details. The whistling noise combined with the EPC light strongly suggests a vacuum leak, very similar to what I experienced on my S6. After replacing both the pressure sensor and fixing the vacuum leak, I noticed immediate improvements: Engine power restored within the first few kilometers, Fuel consumption dropped back to normal, Whistling noise completely gone, Check engine light cleared The ECU did require a quick adaptation procedure after the sensor replacement. The shop used their diagnostic tool to reset the learned values, taking about 15 minutes extra. Worth noting that the engine performance kept improving slightly over the next 100km as the ECU fine-tuned its parameters. Your mileage is actually quite low for this type of failure, but intake manifold issues can develop regardless of mileage, especially if there are vacuum leaks stressing the sensor. The combination of symptoms, whistling noise, EPC light, and engine performance issues, matches the classic signs of intake manifold pressure sensor failure paired with vacuum leaks. Since your car runs the same engine family as my S6, I suggest having both the sensor and the intake manifold gaskets checked. The total repair time and cost should be similar to what I experienced.

Thanks for the helpful information. The whistling sound you mentioned matches exactly what I'm hearing, so I'm now quite confident it's a vacuum leak affecting the MAP sensor. Will get it checked out this week, especially since the symptoms match your experience so closely. Good to know about the ECU adaptation procedure, I'll make sure to mention this to the shop. The 235 Euro cost seems very reasonable for both the automotive sensor replacement and vacuum leak repair. Really hoping this fixes the sluggish engine performance and high fuel consumption I've been experiencing. Quick follow-up: For the first 100km after repair, should I drive normally or keep the revs low while the ECU adapts? Want to ensure optimal engine performance once everything is fixed. Also, did you need to use specific OEM parts for the MAP sensor and intake manifold gaskets, or did aftermarket components work fine?