Bump steer on a 97 ford aspire?

My car when I hit a bump will cause the steering wheel to vibrate and then the car will dart to the left. It does not do it all the time. The shocks, shock mounts, wheel bearings and cv shafts are new. Any ideas on what the problem could be. The ball joints do not seem to have any play in them and the tie rods are parallel to the a-arms and the steering wheel has no play.