The first thing you have to do is identify if your Card Reader is intelligent with Serial RS-232 type output, in which case my program will not be suitable. You must ID the reader and it's connections first, otherwise you're just stabbing blindly in the dark.

With separate Clock and Data lines, the host program syncs to the speed of the Clock signal. This Clock will vary in speed depending how fast a Card is swiped thru the Reader. As I recall, in tests, you couldn't physically swipe a card thru the reader so fast that the host PIC at 4MHz didn't catch it every time.