Q3 Hissing + High Fuel Use Points to Vacuum Leak

Had similar issues with my 2016 A3 2.0 TFSI. The sudden increase in fuel economy and hissing sound typically points to a vacuum leak in the intake system. In my case, the intake hose had developed small cracks near the turbocharger connection, allowing unmetered air to enter the system. The check engine light came on because the engine was getting incorrect air-fuel mixture readings. The Mass Air Flow sensor was detecting less air than actually entering, causing the engine to run rich and waste fuel. The repair involved: Complete inspection of intake system, Pressure testing to locate the exact leak point, Replacing the cracked intake hose, Clearing the check engine codes This was not a severe mechanical issue, but leaving it unfixed can lead to poor engine performance and potential damage to the turbocharger over time. The repair was straightforward and took about 2 hours of labor. Suggest having the intake manifold and all connected hoses inspected, particularly around connection points and bends where cracks commonly develop. Also worth checking the air filter while the system is opened up.

Thanks for your detailed response. You basically described exactly what happened to my Q3. The engine misfire and hissing noise were driving me crazy. I also noticed the vacuum hose was indeed the culprit, with visible wear near the connection points. How much did the whole repair cost you in the end? Just want to double check before heading to the shop. Also, have you experienced any related issues since getting it fixed?

Thanks for asking about the follow-up. After fixing the intake hose leak for 100 Euro, my car has been running perfectly for the past 8 months. The fuel economy returned to normal immediately, and that annoying hissing noise completely disappeared. The throttle body response is much smoother now, and the engine performs exactly as it should. The check engine light cleared up right after the repair and hasnt come back. The turbocharger is also working properly with no unusual sounds. The mechanic showed me the old cracked hose, and it was pretty obvious why it was causing problems. Getting it fixed early definitely prevented more expensive issues down the line. If you notice any similar symptoms in the future, best to check the intake manifold and connected hoses first, they often wear out around the same time.

Thanks for the input. Took my Q3 to a different shop this time and what a difference! The mechanic found the vacuum hose issue right away using their leak detection equipment. Total bill came to 150 Euro including parts and labor, way better than I expected. They showed me the damaged hose and explained how it was affecting the turbocharger performance. Guess the unmetered air was really messing with the whole system. Been driving for about a week now and the car feels completely different. No more hissing noise, normal fuel consumption again, and the engine misfire is gone. Also learned my lesson about regular inspection of these parts to catch issues early. The whole repair took less than 3 hours and saved me from what could have been much bigger problems later. Really glad I asked here first and knew what to expect at the shop.