[sibhusz06]

I just started noticing what I can best describe as a subtle knock that is not perfectly tied to engine rotation. Basically at idle or 600 rpms, I hear what I describe as a knock knock..pause knock knock knock knock...pause knock.. it is not perfectly rhythmic relative to engine speed, rather seems like it comes and goes..

Its very subtle and I can't capture audio but only audible at 650 rpms. If I rev to 800 rpms, it goes away completely and it does not follow engine speed any higher in revs. Ive tried to isolate it and it seems to be coming from the front of the engine around the alternator/ belt drive area but I can't tell if the pulleys are causing this or perhaps its coming from the engine itself.

Any ideas, thanks!..