I have a 2021 1.5 TSI Skoda Octavia petrol with about 53k km. Lately (never really paid attention it, could be that it has always been there) my car has developed this irregular rumbling kind of noise when starting the engine up cold. It's almost as if it sounds like someone is blowing bubbles in a glass of water with a straw. I usually let the engine idle for 2 minutes before driving off in the morning. Else the car is very jerky. It starts at about 1500 rpm and then drops to around 900 rpm in 2 drops. I can also hear it when I take my foot off the clutch pedal without accelerating from a standstill position after the engine has started for 2 minutes. Then it's a more rhythmic sound. I wouldn't say it sounds like knocking, more like as if there's air or exhaust escaping somewhere. After I drive off and start accelerating I can't hear it anymore.

 

It completely disappears when the engine has warmed up. Even when accelerating from a standstil by just letting the foot off the clutch without pushing down on the acceleration.

 

Is this something I should get checked out? I attached a video, but if you want to use headphones or put the volume up loudly, because it's faint in the video. When I'm sitting in the car it's quite audible.

 

Edited 11 September, 20241 yr by PilsnerUrquel

Hi, I have a 2020 1.5 TSI mk4 Octavia.  I too have to wait a few moments after cold starting until the revs drop to 900 rpm (Otherwise the car kangaroos).

Regarding the noise, it could be a hole or break in a plastic pipe connector(s) in the EVAP system, which is located under the plastic engine cover.  It is a recognised fault by Skoda and mine started at about 4 years and 55,000 miles - BTW this has no effect upon cold start kangarooing!

Good luck!