# Knocking sound when tapping the trottle

**URL:** <https://community.cartalk.com/t/knocking-sound-when-tapping-the-trottle/145079>\
**Category:** Maintenance/Repairs\
**Created:** [July 23, 2019, 3:35pm UTC](https://community.cartalk.com/t/knocking-sound-when-tapping-the-trottle/145079 "2019-07-23T15:35:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Alex\_VW\_1337](https://avatars.discourse-cdn.com/v4/letter/a/53a042/32.png) [@Alex\_VW\_1337](https://community.cartalk.com/u/Alex_VW_1337)\
**Post date:** [July 23, 2019, 3:35pm UTC](https://community.cartalk.com/t/knocking-sound-when-tapping-the-trottle/145079/1 "2019-07-23T15:35:55Z")

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Hello guyz , it’s been a while that im noticing weird sound coming from my Tiguan’s 2.0 TDI engine  
So first of all my engine sound changed slightly when im in 1750 - 2000 rpm if im holding the throtlle for 5 - 10 % and it goes back to normal engine sound when throttling a litlle more , also im having a knocking sound when i press the throtlle just a litlle and dissepears instantly this happens in 1200 rpm - 2500 rpm and does not make knock sound in higher rpm , please guys help me to identify the issue and sorry for my bad english … , Thank you .

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**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\
**Post date:** [July 23, 2019, 3:58pm UTC](https://community.cartalk.com/t/knocking-sound-when-tapping-the-trottle/145079/2 "2019-07-23T15:58:02Z")

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A failing fuel injector could cause a knock in a diesel. The way I’ve always checked them is to loosen the fuel supply line at the injector and note if the noise goes away. If it does the injector is failing.