Three frames per second is about as good as you'll find on a camera that costs less than $1000.
Are you sure you're getting the 3 FPS you want?
There are a number of things that can reduce the rate at which the camera can take photos. One, of course, is the speed of the flash memory card, but there are settings that can cause the camera to slow down.
Try setting the camera to manual focus, manual exposure, leave the lens cap on, and hold down the shutter button. If you can't get 30 frames in 10 seconds, your memory card is probably too slow. If you can, take off the lens cap and try the same thing. If you still can, turn on the AE and try again. etc. etc. etc.