There is this sound behind engine like knocking. It can usually be heard when engine is warmed up and idles. When I rev it up that sound completely dissapears. Does anyone know if this is some bad thing or I should just let it be.?

 

Sounds like it needs a valve lash adjustment. Loose noisy valve train.

If sound persists after a proper valve lash adjustment (done with a cold engine). Then investigate further with mechanics stethoscope.

 

I have already done valve lash adjustment two weeks ago... Is it possible to be bad engine mounts?

 

Did it sound like that before your adjustment?

 

It started two weeks after valve adjustment.

 

I would redo your adjustment. It's possible (especially if you didn't torque to spec the locknuts) that some of the valves loosened up.

Do you have the factory service manual for all the specs for the valve lash adjustment?