RS4 MAP Sensor Issues Killing Performance and MPG

Had the exact same symptoms on my 2021 RS5 last winter. As someone who regularly does basic maintenance, this was beyond my usual DIY comfort zone. The manifold pressure sensor readings were all over the place, causing similar issues, sluggish acceleration, terrible fuel economy, and check engine light. Initially thought it was just the MAP sensor failing, but the workshop discovered a significant vacuum leak in the intake manifold system. The automotive sensor itself was actually fine, the real problem was a cracked vacuum line that was throwing off all the pressure readings. Total repair came to 235 Euro, including diagnosis and replacement of the damaged components. Key learning: When the MAP sensor shows issues, always have the entire intake manifold system checked for leaks. The manifold pressure readings can be thrown off by various issues beyond just sensor failure. What engine variant does your RS4 have? Would help to know if youre seeing any specific error codes. Also, have you noticed if the symptoms get worse during cold starts or when the engine is at operating temperature?

Thanks for sharing your experience. My warranty is still active at 51109KM, and I just had the 50000KM service done last month. The error codes point directly to the MAP sensor but I will have them check the entire intake manifold system based on your feedback. My symptoms are consistent regardless of engine temperature, which seems different from your case. The pressure sensor readings are completely erratic according to my OBD scanner. I will book it in for a proper diagnosis since several others mentioned similar vacuum line issues. Better to get it checked while still under warranty.

Worth mentioning that after my vacuum line issue, I installed an aftermarket OBD monitoring system to keep a closer eye on MAP sensor readings. If your car displays consistently erratic pressure sensor values regardless of temperature, it actually sounds more like a direct sensor failure than what I experienced. My symptoms definitely varied with engine temperature, the vacuum leak would cause more noticeable issues during cold operation. Your consistent readings suggest the MAP sensor itself might need replacement. Since youre under warranty, getting a full intake system inspection is the smart move. Just make sure they document all the car sensor testing thoroughly. When automotive sensors fail during the warranty period, some manufacturers try to claim external damage or modification voided coverage. Looking at the car repair records from my experience, pressure sensor problems often start subtle before becoming more obvious. Good call getting it checked early rather than waiting for complete sensor failure. Keep us posted on what they find, would be interesting to compare if its truly a different root cause than my vacuum line issue. These intake manifold problems can be tricky to diagnose without the right diagnostic equipment.

Thanks for the detailed follow-up. The service appointment is scheduled for next week to investigate the engine performance issues. I ran another scan and the error codes still point to the MAP sensor, but after hearing similar stories about vacuum leaks causing manifold pressure problems, I want them to do a complete system check. Since the symptoms are constant regardless of temperature, my gut feeling is that its a faulty sensor rather than a vacuum issue. The warranty should cover everything since the car just had its major service and all maintenance is documented. Will make sure they fully test the intake manifold system and sensor readings before replacing any parts. Appreciate everyones input on checking the vacuum lines even when sensor failure seems obvious. Will update once I get the final diagnosis and repair completed.