Idiling problem /jerking forward while in motion

The last shop told me the problem is a bad cam. I grabbed an upper and lower cam from a 96 from the junk yard. When I opened the value cover I didn't see any difference or worn metal. I replaced both cams anyway but problem still exists and is getting worst. Stalls and jerk forward while in motion.
Any suggestions?
If it was just a tune up I think the shop would have handled it.