RS3 Turbo Hissing + High Fuel Use Needs Urgent Check

Had similar issues on my S4 2016 with the same symptoms. The check engine light triggered due to a leak in the air intake system. The hissing noise during acceleration was a clear sign of air escaping between the turbocharger and throttle body assembly. The issue turned out to be a cracked intake hose, which caused incorrect air-fuel mixture readings and increased fuel consumption. The leak detection test confirmed multiple small cracks in the rubber section where the hose connects to the turbocharger housing. This is not a major repair if caught early, but leaving it unfixed can lead to turbocharger damage and poor engine performance. The turbocharger needs proper pressure to function correctly, and any air leak compromises its efficiency. The repair involved replacing the intake hose assembly and checking all surrounding clamps and connections. After the fix, fuel consumption returned to normal and the hissing noise disappeared completely. The check engine light cleared after the system regained proper pressure. Would suggest getting it diagnosed soon, as running the engine with intake leaks can cause more expensive problems over time.

Thanks for sharing your experience. That explanation about the intake system matches my symptoms exactly. The hissing and increased fuel consumption started about 2 weeks ago, and just like your case, the check engine light has been inconsistent. Do you remember roughly what you paid for the vacuum hose replacement and diagnostics? Also wondering if youve had any engine misfire issues or other problems since getting it fixed. Just want to make sure Im prepared for what the repair might cost and if I should look out for related issues.

Good news, since fixing the vacuum hose issue on my S4, everything has been running perfectly with no engine misfires or other problems. The total repair came to 100 Euro, which included the diagnostic test and replacing the cracked intake hose near the turbocharger. The air intake system leak was causing all those symptoms, the hissing, poor fuel economy, and the erratic check engine light. Once the intake manifold connections were properly sealed, the engine went back to running smoothly and efficiently. The mechanic also inspected the rest of the turbocharger system while doing the repair and confirmed no additional damage had occurred. Getting it fixed early definitely prevented more expensive issues from developing. My fuel consumption returned to normal immediately after the repair. Its been 6 months since the fix and the car performs like new again. No check engine lights or strange noises have returned. The repair was straightforward and definitely worth getting done promptly.

Thanks everyone for the helpful replies. I finally got the car checked out yesterday and wanted to share my experience. The diagnostic confirmed a leak in the vacuum hose system, exactly as suspected. The hissing noise was indeed coming from a crack in the intake hose near the throttle body. The total repair cost was 120 Euro, slightly more than expected because they found another small leak during their thorough leak detection test. The mechanic showed me the damaged parts and explained how the faulty seals were affecting fuel economy. After the repair, the difference is incredible, no more hissing, the check engine light is off, and a quick drive showed the fuel consumption is back to normal. The throttle response feels much smoother too. Really glad I caught this early before it could damage the turbocharger. A big thanks to this forum for helping me understand the issue before the repair. It made the mechanic visit much less stressful knowing what to expect.