T-Roc Intake System Issues: Hissing and Poor MPG

Had a similar issue with my 2020 VW Tiguan last summer. The symptoms match exactly what I experienced, poor fuel economy, hissing noise, and check engine light. After some basic troubleshooting, it turned out to be a cracked intake hose right before the throttle body. The repair was straightforward, took it to my regular workshop where they performed a leak detection test to confirm the exact location. Total cost was 100€ including parts and labor. Definitely worth fixing promptly since intake leaks can cause engine misfire and long-term performance issues if left unchecked. What engine variant does your T-Roc have? This would help determine if the common failure points are similar to what I encountered. Also, have you noticed any specific conditions when the hissing sound is most prominent? This information could help pinpoint the exact location of the potential leak. The repair made a noticeable difference, fuel economy returned to normal and the engine ran much smoother. Just make sure to have a proper diagnosis done first, as similar symptoms can sometimes point to other issues in the intake system.

Thanks for sharing that experience. I also recently noticed this exact problem at 41072km. After reading about your repair cost and diagnosis process, I feel more confident about what to expect. The hissing is most noticeable during hard acceleration, especially when merging onto faster roads. Good point about the vacuum hose possibilities, I will get that checked too when I bring it in. The air intake system on these 2022 models should still be under warranty, which is a relief. I noticed the drop in fuel economy right after my latest service, which makes me wonder if something got knocked loose during maintenance.

Thanks for the follow-up. After fixing the cracked vacuum hose on my Tiguan, I actually had a similar issue resurface about 6 months later. This time it was a loose clamp connecting the turbocharger to the intake manifold that caused identical symptoms. The timing of your symptoms appearing after service is interesting, I had the same experience. The intake system components can be sensitive to handling during routine maintenance. Sometimes the connections just need proper retightening. Since your vehicle is still under warranty, definitely have them check all the connections around the turbocharger and intake manifold assembly. My fuel economy dropped by about 15% before getting the loose clamp fixed. The hissing during hard acceleration is a classic sign of boost leak in these engines. Quick tip, while they have it in for warranty work, ask them to inspect all the small vacuum hoses too. These can deteriorate or come loose and cause the same symptoms, but might not be immediately visible during a basic inspection.

Thanks for all the detailed feedback about vacuum hose and air intake issues. The parallels between your Tiguan experience and my situation are really helpful. I will definitely request a complete inspection of all connection points during the warranty check, particularly around the turbocharger and intake manifold area. The loose clamp issue you mentioned seems very plausible given the timing after my service. After discussing this, I am almost certain there is an air leak causing my check engine light and performance problems. I will schedule the warranty inspection this week and make sure they do a proper leak detection test, focusing on both the main intake components and those smaller vacuum hoses you mentioned. Really appreciate the heads-up about checking all the connections, would have hated to fix one issue only to have another loose connection cause problems later. Will update once I get it looked at, but feeling much more informed about what to expect during the diagnostic process. The 15% fuel economy drop you mentioned matches almost exactly what I am seeing, which further confirms we are likely dealing with the same type of problem.