VW Touareg TDI Turbo Issues: Whistling and Power Loss

I had similar issues with a 2005 VW Phaeton TDI last year. With some experience working on turbo systems, I can relate to these symptoms. The engine light, power loss and whistling sound matched exactly what I encountered. After checking the intake manifold myself, I finally took it to a workshop when the jerking during acceleration became worse. The actual problem turned out to be much simpler than expected, a loose connection at the turbocharger pressure sensor. The cable had worked itself loose over time, causing erratic readings. The workshop did a thorough check of the entire turbo system and found the faulty connection was causing the ECU to get incorrect boost readings. Total repair cost was 95€, mainly labor for diagnostic work and fixing the connection. The turbocharger itself was perfectly fine. Since the repair, no more engine light issues and the power delivery is smooth again. To better assist with your case, could you share: Any diagnostic codes from the engine light? When did these symptoms first appear? Have you noticed any unusual exhaust smoke? Was there any recent work done on the turbo system? Getting this additional information would help determine if you are dealing with a similar connection issue or something else in the turbo system.

Last service was at 120000km and I already tried checking for loose connections around the boost sensor area but everything seems properly connected. The symptoms started gradually over the past 2 weeks. No diagnostic codes available yet as I need to schedule a proper check. No recent work on the turbo system but I notice black smoke occasionally when accelerating hard. The whistling sound is most noticeable between 2000-3000 rpm. The check engine light started flashing more frequently this week which is why I am getting concerned about potential engine damage. The boost sensor theory makes sense but I noticed the air intake hose has some minor cracks that might also explain the hissing noise. Thanks for the detailed feedback about the pressure sensor connection. I will get it properly diagnosed but wanted to gather some real experiences first.

Those symptoms with the black smoke and hissing definitely point beyond just a boost sensor issue, based on what happened with my Phaeton. After your details about the cracked air intake hose, this sounds more like a boost leak situation. The cracks you mentioned in the air intake hose can cause exactly these symptoms, the whistling noise and power loss match what you would expect from a boost leak. The black smoke typically indicates the engine is running rich to compensate for the leak. When my turbocharger system had issues, I also noticed similar cracking in the rubber hoses. These wear points create boost leaks that throw off the entire system. The engine light started flashing more frequently as the cracks got worse. A proper boost leak test would confirm this, it cost around 150€ at my workshop, but saved me from unnecessarily replacing the boost sensor. The intake manifold and all connecting hoses should be pressure tested to find all potential leak points. If the hoses are original at 120000km, it might be worth replacing the full set while they are checking the system. This solved both the whistling and the power issues in my case.

Appreciate the detailed response about boost leaks. I will get the hoses pressure tested before replacing any sensors. The connection between black smoke and boost leaks makes a lot of sense now, I noticed the smoke gets worse when pushing the engine harder, which fits with what you described. My main concern was potential turbocharger damage, but it sounds like catching these air intake issues early should prevent that. Will have the workshop do a complete inspection of the turbo system and replace any worn hoses. The flashing check engine light has gotten more frequent over the past few days, so I will book it in this week rather than risk more problems. Good to know a boost leak test costs around 150€, much better than replacing parts unnecessarily. Thanks for sharing your experience with similar symptoms. Having dealt with the same whistling noise and performance issues, your feedback really helped narrow down where to look first. Will update once I get the proper diagnosis and repair done.