A1 Manifold Sensor Issues Cause Power and MPG Drop

Had a very similar issue with my A3 2016 last summer. As someone with moderate experience working on cars, I initially thought it was just a dirty MAP sensor that needed cleaning. The symptoms matched exactly what you describe, sluggish acceleration, higher fuel consumption, and the engine light staying on. After scanning, it showed the manifold pressure readings were inconsistent, pointing to either a sensor failure or vacuum leak. Took it to my regular workshop where they performed a smoke test and discovered a significant vacuum leak near the intake manifold. The MAP sensor itself was actually fine, but the faulty seal was causing incorrect pressure readings. Total repair came to 235 Euro including parts and labor. Before jumping to conclusions about sensor failure, you should: 1. Get the error codes read first 2. Have them check for vacuum leaks 3. Test the MAP sensor output Would you mind sharing: Current mileage, Any recent repairs or maintenance, Specific error codes if you have them, Whether the problems started suddenly or gradually This information would help determine if your issue is similar to what I experienced with my A3 or if its something else entirely.

Thanks for the comprehensive advice. My current mileage is 132007 KM and the last major service was a timing belt replacement 6 months ago. The problems started gradually over the past month. The engine performance issues seem very similar to what you experienced. A vacuum leak causing incorrect sensor readings makes sense given how the symptoms developed. The intake manifold area on these engines is known to develop seal issues. Will definitely get those error codes read before assuming sensor failure is the root cause. Good point about the smoke test, seems like a logical first step to check for any vacuum leaks affecting the manifold pressure readings.

Glad your symptoms match what I experienced with my A3. The timing belt service timing is interesting, in my case, I noticed the vacuum leak developed about 8 months after major work around the engine. When mechanics handle components in that area, seals can sometimes get stressed or slightly displaced. The gradual onset suggests a slowly deteriorating seal rather than sudden MAP sensor failure. Car sensors typically fail more abruptly. When my manifold sensor was reading incorrectly due to the vacuum leak, the values would fluctuate more as the engine warmed up. One other quick check, verify if the idle is stable or fluctuating. In my case, the idle would occasionally drop or surge slightly, especially when the engine was fully warm. This helped confirm it was a vacuum issue affecting the pressure sensor readings rather than a faulty sensor itself. The repair on my A3 not only resolved the check engine light and power issues but brought fuel consumption back to normal. The smoke test should quickly reveal if you have the same root cause. Just make sure they check all vacuum lines and seals around the intake manifold thoroughly. Let us know what the diagnostic results show. If it is indeed a vacuum leak like my case, the fix should be relatively straightforward and much cheaper than replacing sensors unnecessarily.

Your advice about checking the vacuum lines makes a lot of sense. I checked with my local shop and scheduled a diagnostic appointment for next week. They quoted 80 Euro for a complete diagnostic including the smoke test you mentioned. The idle behavior you described matches my situation perfectly, it does surge slightly when warm. That detail about vacuum leaks typically showing up months after major work is particularly relevant given my recent timing belt service. I will definitely get those manifold pressure readings checked before replacing any automotive sensors. Your experience helps narrow down the most likely cause, saving time and potentially unnecessary parts replacement. Based on the similar engine performance issues and circumstances, I suspect Ill also find a vacuum leak rather than actual sensor failure. Will post an update once I get the diagnostic results and know exactly what is affecting the MAP sensor readings. Thanks again for sharing your repair experience in such detail.