Audi S5 MAF Sensor Failure Causing Multiple Issues

Had exactly these symptoms with my 2015 Audi S4. The check engine light came on and fuel economy dropped significantly. The idle was unstable and the engine would stall, especially after cold starts. A MAF sensor failure diagnosis proved correct. The symptoms match perfectly, increased fuel consumption, rough idle, and visible smoke are classic signs of a mass air flow sensor malfunction. In my case, the sensor was not reading the incoming air correctly, causing the engine to run rich. The repair was straightforward but required specific diagnostic equipment to verify the MAF sensor failure. After replacement, the engine performance returned to normal immediately. This is a serious issue that should not be ignored, as continuous running with a faulty MAF sensor can damage other components like catalytic converters. First tried cleaning the sensor, but that only helped temporarily. Full replacement was ultimately needed. The repair prevented potentially more expensive issues down the line. A qualified Audi technician should be able to confirm the diagnosis with proper testing equipment. Given your mileage, this is a common maintenance point for the MAF sensor to need replacement.

Thanks for sharing your experience with the S4. My S5 had very similar issues last year, check engine light, bad fuel economy, and constant stalling. Really sounded familiar reading your detailed response about the mass air flow sensor problems. The air filter was actually quite dirty when they checked it, which apparently contributed to the sensor failure. Would be curious to know how much you ended up paying for the full fix? Did you have any other issues pop up afterwards? Want to make sure I budget properly if I need to get mine looked at again.

After getting the mass air flow sensor replaced last year, my S5 has been running perfectly. The complete repair, including labor and new sensor, came to 365 Euro. The mechanic confirmed the MAF sensor failure was the root cause of the engine stalling and poor fuel economy. The dirty air filter definitely contributed to the sensor issues. Always worth doing regular air filter checks to prevent similar mass air flow problems. Since the fix, fuel consumption returned to normal and the stalling completely stopped. No additional problems have surfaced in the past year. The repair cost was worth it considering how much extra fuel I was burning with the faulty sensor. Just make sure you use a qualified technician who can properly diagnose and calibrate the new MAF sensor. Regular maintenance and keeping the air filter clean should prevent this issue from recurring. The improved performance and fuel economy after the repair made it clear the mass air flow sensor was the culprit.

Finally got my S5 checked out yesterday after reading all the responses here. You guys were spot on, it was definitely the MAF sensor causing all the trouble. The mechanic found the air-fuel ratio was way off and the dirty air filter had damaged the sensor over time. Total bill came to 410 Euro for parts and labor, bit more than expected but worth every cent. The check engine light is gone, no more stalling, and fuel economy is back to normal. The mechanic showed me the old sensor, it was pretty contaminated. The car runs like new now. No more smoke on acceleration and idle is perfectly smooth. Learned my lesson about regular air filter maintenance the hard way. Really glad I caught this before it caused more expensive problems with the engine. Thanks again for helping me diagnose this correctly before heading to the shop. Saved me from getting unnecessary repairs or making the problem worse.