sounds like a rod knock on startup but quiets after idle down. what gives and can this be a big problem? 75000 mi.

 

There is a rubber hose that is plugged into the passenger side valve cover it runs behind the Intake manifold and plugs into a vacuum line on the drivers side this thing gets hot and dry rots it causes a minor vacuum leak I replaced mine with some hose from napa for around $3 it should fix your issue

 

Its a lifter. When u leave it sit for a bit it looses pressure so when u start it its tapping till the oil pressure gets built back up. It prob only taps for a few seconds. But a bad lifter can lead to other problems so its best to replace it as soon as you can