About 2 weeks ago, my VW tech did a carbon clean on my CC's intake manifold (only 44k miles). Since then, I've been hearing this loud whistle\chirping noise whenever I accelerate the car. It only happens during acceleration. I tried replicating the problem when the car is parked but I don't hear that weird noise at all. I notified the tech and he said it could be a bad diverter valve. He replaced that today and still the noise is there when I accelerate. I know the mechanic removed the air box and air intake when he did the carbon clean. I've checked all the hoses and clamps and they look to be in place correctly. The VW tech said it's a possible turbo issue but he's not sure. The engine runs smooth, no loss of power, no engine light. Only that weird noise.
My guess was going to be the diverter valve but if that's already been replaced then I'd be leaning towards a vacuum leak or boost leak in or around the intake or throttle body where he worked. All of the hoses clamps are good and tight?
If you have a loud whistling noise coming from your 2.0t TSI engine you might have a bad PCV valve. A bad PCV can also cause Fault code 0171 System Too Lean, as well as others. Take a look HERE for more info on the TSI PCV issues. http://shopdap.com/common-problems-2-0t-tsi-engine/
Yeah these days mechanics aren't very good at trouble shooting something that doesn't have a code to tell them where to look. He should try using carb cleaner or starter fluid.
Update. The mechanic said he already replaced the PCV unit. So far, he's replaced the diverter valve and PCV but the noise is still there. I'm starting to think it could be the high pressure fuel pump because the noise sounds a lot closer on my side than the passenger. I managed to record a short video of the sound while driving. If you listen carefully, you'll hear a whistle\chirping noise when I accelerate. The mic on my phone is sensitive and it picked up a lot of road noise as well. Sorry folks.
It's the turbo. VW mechanic finally called me and found the root cause. He recommended that I contact the dealer since it's part of the emission warranty (7 years or 70,000 miles).
Just got the car back from the dealer today. The waste gate was malfunctioning. They replaced the turbo. Car is running fine now. Didn't cost me anything. It was part of the emission (pzev) warranty.
FYI. Turbo diverter valve and PCV are also part of VW's pzev warranty.
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