I have an annoying rattle sound when the car is at 1200-1800 RPM only. I had someone look at the cat heat sheild and exhaust manifold and neither was the culprit. Does anyone have any ideas as to what may be causing this rattle. It sounds like a CV joint but will rattle at a stand still. A friend says it's the water pump but that was replaced 3000 miles ago. Any help would be greatly appreciated.

 

Does it go away once the car warms up a bit?

 

Nope it gets worse.

 

Without hearing the actual sound, we can only guess at the source. It could be your exhaust, your skid plates, a motor mount, axles contacting something, heck even your dual-mass flywheel failing can cause gear lash in the transmission, manifesting as a rattle. There is a lot of heat-shielding in the car - follow the exhaust/axles/driveshaft from the engine to the rear bumper and look for any signs of contact.