E39 strange engine knock noise? m52b28tu

[BrianE39 0]

Hey guys,

Recently I found out when i start the car in the morning (forgot to mention that the car also have rough idle when cold start)

the engine sound become more louder then i take a look deeply

I found out that there is some strange knock noise coming from Intake Manifold

whats wrong with it??

I have check for DISA valve but the sound dont go away when i unplug it ??

Here is the video i taken this morning :

my car is E39 1999 528i M52B28TU

[central3 31]

Very hard to tell from the video but my old E46 330 had a faulty DISA unit. It had a deep knocking noise at idle - $502.14 to replace - ouch but fixed it