My car has been running properly for about 2 weeks now. But yesterday there was a little rumble. I thought it was a loose pulley. I started it up today and the idle dropped and now the rumble is pretty loud. It sounds like something metal is rattling around in the head or in one of the cylinders. Anyone ever had this problem before? The car sat for four years before I got it if that helps.

 

ive had a rocker arm pop off once.. and yeah it was pretty bad.. exhaust valve o one of my cylnders didnt open and i pretty much had to rebuild the engine... pop off the valve cover and take a look..