I have a 99 CL and have noticed that it makes a rattling noise (sounds like metal on metal making a tapping noise) when the engine is cool. At first I thought the muffler was loose, but then realized that it only happens when it first starts. This happens while idling and going into first gear. Not sure if it does it at higher gears/speeds as well, but I don't hear anything. Car is otherwise in great condition. Has 150K mis. on it, fyi. It mainly does it when u rev the engine at the lower speed and/or at idle. Anyone know what I should check out to find the source of the problem?