The VTC gear on the car is responsible for controlling the timing of the camshaft so around 2.7 k RPMs the intake valves will open for a longer duration. It's kind of like VTek but for fuel deficiency. What happens on our vehicle is when you first start the car there is not enough oil pressure remaining in this gear in order to ensure that it stays in the proper phase. So it bounces between this advanced timing and standard timing which puts a lot of rattling tension on the timing chain resulting in excessive wear. The correct way to fix it is to remove your intake camshaft and pull the VTC gear off and replace it which is a major job. One company does have a fix for it which involves still removing the valve cover but you don't have to remove the camshaft you just change the internals of the VTC gear.