VW Touran Air Leak: Symptoms & Fuel Economy Issues

I faced nearly identical issues with my 2020 VW Tiguan. Having some experience with basic car maintenance, I first noticed similar symptoms, poor fuel economy and that distinct hissing sound during acceleration. After performing basic vacuum hose checks at home, I discovered a leak in the intake system. The engine misfire symptoms and increased fuel consumption were clear indicators something was wrong with the air intake. The workshop confirmed my suspicions using proper leak detection equipment. They found a damaged air intake hose that was causing unmetered air to enter the system. The repair involved replacing the faulty hose and checking the air filter while they were at it. Total cost came to 100€ including parts and labor. Before you proceed with repairs, could you share: Current mileage on your Touran, Whether the hissing noise changes with engine RPM, If you notice any other unusual engine sounds, When was your last air filter change This information would help determine if your issue matches what I experienced. These symptoms often point to intake system problems, but its best to have a proper diagnosis to avoid unnecessary repairs.

Thanks for the detailed advice. My current mileage is 42804km and my last service was done at 40000km where they replaced the air filter. The hissing noise definitely gets louder with higher RPM, particularly noticeable above 2500 RPM. The intake manifold seems to be the source of the noise based on where I can hear it coming from. The check engine light stays solid, not flashing, which I understand might indicate its not causing severe engine misfire issues yet. Since the air filter is relatively new, Im thinking the leak might be somewhere else in the air intake system. Would using soapy water around the connections help locate any vacuum leaks before I take it to the workshop?

Thanks for providing those details about your Touran. Similar to what happened with my Tiguan, the RPM-dependent hissing noise strongly points to a vacuum leak in the intake system. Using soapy water for leak detection can work, but be extremely careful not to let any water enter the intake system. I learned from my experience that a safer method is to inspect all vacuum hoses visually first, look for any cracks, loose connections, or deterioration. Focus especially on the areas around the intake manifold where the hissing seems loudest. When my Tiguan had these symptoms, the solid check engine light also indicated a non-critical issue. The workshop later confirmed that unmetered air was causing poor fuel economy but wasnt severe enough to trigger serious engine misfire conditions. Since your air filter is new, I would suspect either: A loose or damaged vacuum hose connection, A cracked intake boot, A failing intake manifold gasket Given the mileage matches when my issues started (around 45000km), and considering the similar symptoms, I would recommend getting it checked soon before it affects fuel economy further. The repair cost might be similar to what I paid if its just a vacuum hose issue.

Thanks for sharing those repair experiences. After your comments, I suspect my Touran is experiencing very similar vacuum hose issues. The matching symptoms with your Tiguan case, especially the RPM-dependent hissing and increased fuel consumption, make me more confident about the likely diagnosis. I will start by doing a careful visual inspection of the vacuum hoses and connections around the intake manifold, being cautious not to risk any water damage during leak detection attempts. Since my car has comparable mileage to when your issues developed, and given the matching check engine light behavior, I feel better prepared for my workshop visit. Will get it checked soon to prevent any potential engine misfire situations from developing. The 100€ repair cost reference is helpful for budgeting. Having narrowed down the probable causes makes me more informed when discussing the repair options with the mechanic. Appreciate the thorough guidance on diagnosing these turbocharger and intake system issues.