S7 Vacuum Leak Alert: Turbo Area Hissing Issues

I had a very similar issue with my 2014 Audi S6. As someone with some experience working on cars, I initially tried diagnosing the issue myself before taking it to a workshop. The symptoms matched exactly what you described, poor fuel economy, hissing noise, and reduced engine performance. After inspection, the workshop found a crack in the intake hose near the turbocharger connection. The leak detection test confirmed multiple small tears that were causing air to escape. The repair was straightforward, they replaced the damaged intake hose and performed a thorough check of the surrounding components. Total cost was 100 Euro including parts and labor. The engine misfire issues cleared up immediately after the repair, and fuel economy returned to normal. To help diagnose your specific case, could you share: Have you noticed any specific driving conditions when the hissing is more pronounced? Did the issue develop gradually or suddenly? Has your air filter been replaced recently? Are there any other warning lights besides the check engine light? These details would help determine if your issue is similar to what I experienced with my S6.

My car has 110751 KM and started having this hissing noise about 2 weeks ago. The sound is most noticeable during hard acceleration, especially when the turbocharger kicks in. The engine misfire seems to happen more frequently during cold starts. I have not replaced the air filter since my last service 8 months ago. The only warning light is the check engine light, which started flashing occasionally before staying on permanently. The engine also feels more sluggish than usual, particularly when accelerating from a stop. A complete vacuum hose inspection makes sense as the next step, along with checking the air intake system components around the turbocharger. Would replacing the air filter be a good first step before diving deeper into the diagnosis?

Based on your description, this sounds very similar to what I dealt with on my S6. The location of the hissing and its correlation with turbocharger engagement strongly suggests a vacuum hose or air intake issue near the turbo system. The flashing check engine light and cold start misfires are particularly telling. When I had my issue, these symptoms developed in almost the same pattern. While replacing the air filter is good maintenance, I would not expect it to resolve these specific symptoms. From my experience, you should focus on: 1. The vacuum hoses connecting to the throttle body 2. The main air intake tube running to the turbocharger 3. The intercooler connections 4. The boost pressure sensors and their connections The sluggish acceleration you mention was also present in my case, caused by the engine getting incorrect air-fuel mixtures due to the leak. The workshop found that the engine misfire was directly related to the compromised air intake system. The repair in my case involved: Pressure testing the entire intake system, Replacing the cracked vacuum hose, Checking all turbocharger connections, Clearing the engine codes Given the similar symptoms and mileage, I would recommend having these areas inspected before replacing the air filter. The flashing check engine light particularly suggests this needs attention soon to prevent potential damage to the catalytic converter.

Thanks for the detailed response. The symptoms you described with your S6 match my situation perfectly, especially regarding how the hissing noise correlates with turbo engagement. I will skip the air filter replacement for now and focus on having the vacuum system tested first. I scheduled an appointment with a workshop that specializes in turbo systems. They will perform a complete pressure test of the air intake system and inspect all vacuum lines near the throttle body. Makes sense to check the intercooler connections and boost pressure sensors while they are at it. The fact that your fuel economy and engine performance returned to normal after fixing the vacuum leak is encouraging. Hoping my repair will be equally straightforward. Will update once I get the diagnosis, but your experience has helped narrow down where to look first. The flashing check engine light definitely convinced me not to delay getting this checked out.