SQ8 MAP Sensor Failure Causing Performance Drop

Had a similar issue on my 2018 S7 last winter. With some basic experience working on cars, I initially thought it was just the manifold pressure sensor too, but it turned out to be more complex. The symptoms matched exactly what you describe, check engine light, power loss, and that sluggish feeling during acceleration. After taking it to my regular workshop, they discovered a significant vacuum leak in the intake manifold system. The pressure sensor readings were off because of the leak, not because of a faulty automotive sensor. The fix included replacing some cracked vacuum lines and resealing parts of the intake manifold. Total repair came to 235 Euro, which included diagnostic time and parts. Before jumping to conclusions about sensor failure, what specific error codes are you getting? Also, have you noticed any unusual sounds, particularly a hissing noise, when the engine is running? These details would help determine if you are dealing with a similar vacuum leak issue or an actual sensor problem. Can you share more details about: The exact error codes, Any unusual engine sounds, When the symptoms first appeared, Whether the issues are constant or intermittent, If the problem gets worse during specific driving conditions

Thanks for the detailed response. My SQ8 now has 153764 KM and I am getting the P0299 error code consistently. No hissing sounds noticed, but the manifold pressure sensor readings are way off according to my OBD scanner. The issue started gradually over the past 2 weeks and gets notably worse during highway acceleration. I checked the intake manifold closely and found no visible vacuum leaks. The symptoms remain constant regardless of driving conditions, though more pronounced under load. Might book a pressure test to rule out any hidden vacuum issues before replacing the sensor. Last service was done 5000 KM ago and included air filter replacement, which makes me wonder if something was disturbed during that work.

Thanks for the update on your SQ8. After dealing with my S7s sensor issues last year, I can share some relevant insights. The P0299 code does point more specifically toward a manifold pressure sensor problem, unlike my case where the vacuum leak was the root cause. Since you have already checked for vacuum leaks and the symptoms are consistent, sensor failure seems more likely in your situation. When my automotive sensor eventually needed replacement a few months after the vacuum fix, I noticed similar symptoms, constant power loss and poor engine performance regardless of conditions. The fact that your issues started after a service involving air filter replacement is noteworthy. Sometimes disturbing these components can affect sensor calibration or damage connections. The OBD readings showing incorrect pressure values strongly suggest a sensor replacement might be necessary. In my experience, a faulty pressure sensor typically costs around 180 Euro to 250 Euro including installation. Before proceeding with the repair, consider: Testing the sensor wiring connections, Checking for any debris around the sensor, Verifying MAP sensor voltage readings, Confirming proper intake air filter installation Monitor your engine performance closely, as running with incorrect pressure readings can impact long-term reliability.

You are right, I should double-check those connections before committing to a full sensor replacement. The price range for manifold pressure sensor repair seems reasonable, and I want to be thorough before spending money on parts. I will test the wiring and verify the voltage readings on my next day off. Also planning to remove and inspect the air filter installation since that was the last component touched during service. If the automotive sensor tests confirm a failure, at least I will know I covered all bases before the repair. The consistent P0299 error and OBD readings do make sensor failure seem likely, especially since I found no vacuum leaks. Will update the forum once I complete the testing and know the actual cause. Thanks for sharing your experience and helping me narrow down the diagnostic approach.