Hello!

I recently purchased a 172k km om651 w204.
It has had the chain tensioner replaced with the updated version, new oil, new intake all oem.
For 25 seconds after a cold start you can hear the "coicoicoicoicoi" sound before it quiets down significantly.
Please ignore the other rattles as they come from the intake plastic piece.
There are no codes, exhaust is perfectly clean, runs great.
Don't know if it's related but one more issue it has - the idle is not stable when cold, engine feels like hanging for a split second and then overcompensates driving the needle up a tiny bit - for this I already ordered a new fuel pressure regulator.

What is this noise?

 

tc 0 support, thanks