SQ5 Turbo Hissing + High Fuel Use Points to Vacuum Leak

As a 2015 Audi S4 owner, I encountered nearly identical symptoms. The hissing sound combined with increased fuel consumption points strongly to an intake leak, which was confirmed through leak detection testing at the garage. The main culprit was a cracked intercooler hose where it connects to the turbocharger. This vacuum leak caused the engine to run rich, explaining the high fuel usage. The flashing check engine light indicated engine misfire, which happens when the air-fuel mixture gets disrupted by these leaks. The repair involved replacing the intercooler hoses and complete inspection of the turbocharger system. While the work itself wasnt extremely complex, accessing the components required removing several parts, including the air filter housing and front bumper components. This is a fairly serious issue that should be addressed promptly. Running the engine with a significant vacuum leak can potentially damage the turbocharger and cause further performance issues down the line. The symptoms match perfectly with what I experienced, when boost pressure builds up during acceleration, the hissing becomes more pronounced through the compromised hose connection. Recommend getting a proper diagnostic done specifically checking intake system pressure and turbocharger operation before the problem escalates.

Thanks for sharing your experience. My case turned out to be the same, a cracked intercooler hose causing a vacuum hose leak. Glad I fixed it when I did, since the mechanic mentioned it could have led to bigger turbo issues. The engine misfire warnings stopped immediately after the repair. Would you mind sharing what the total repair cost was in your case? Also curious if youve had any fuel economy issues or similar problems since getting it fixed?

Got my Audi S4 fixed last week and the results have been great. The air intake system leak was causing those exact same problems, but after replacing the damaged intake hose everything runs smoothly now. The total repair came to 100 Euro, which seems reasonable considering the potential damage it could have caused to the turbo. Fuel economy has returned to normal and the engine misfire warnings have completely disappeared. The engine runs much smoother without that annoying hissing sound. My air filter was also checked during the repair and it was clean, so that wasnt contributing to the problem. Since the fix, I havent experienced any vacuum hose issues or other related problems. The check engine light hasnt come back on either. Getting this addressed quickly was definitely the right call rather than risking more serious engine damage. The key was finding a mechanic who properly diagnosed the intake system leak instead of guessing at the problem. Would definitely watch out for similar symptoms in the future since these hoses can degrade over time.

I took it to a specialized shop last Thursday after reading your response. The diagnosis confirmed exactly what you described, a vacuum hose leak at the intercooler connection. The throttle body response feels much smoother now that its fixed. The total repair cost was 850 Euro, including parts and labor. The mechanic showed me the cracked hose and explained how the turbocharger system works. He also checked the air filter while everything was apart, which thankfully was still in good condition. My fuel economy has improved dramatically since the repair. The car now uses about 2 liters less per 100km. No more hissing sounds during acceleration and the check engine light has stayed off. Really glad I caught this before it caused any damage to the turbocharger. Good to know these symptoms are fairly common. Will definitely keep an eye on the vacuum hoses during future maintenance checks. Thanks again for pointing me in the right direction.