I replaced the cap and rotor on my 99 4dr 2wd and now I can hear a kind of grinding noise when at an idle. Over the engine noise I can kind of guess that it's coming from the cap and rotor, from inside the truck it sounds like it's coming from right behind the dash. I never heared it until I changed the cap and rotor, I used a borg warner cap and borg warner rotor from Kragen. At first I thought maybe it was just the rotor rubbing on the contacts in the cap and it would eventually bed in and go away but it's been about 3 weeks now and it's still making noise, it still runs good but I don't want the rotor to break off or snap one of the pins in the cap.

Any ideas what I may have done wrong when I changed the cap and rotor besides throwing away the old cap and rotor?

 

I'd pull off the cap and inspect for rubbing.
Just make sure that when you install the rotor that it's all the way down and when you put the cap on that it's in exactly the right spot also.