2000 Silverado windshield wipers with excessive movement?
 

Hi,

I have a 2000 Silverado 1500, ext. cab, 4x4, 5.3 L, auto., and when I have my windshield wipers on, they do this pop up thing to get back to there starting point. It's especially obvious when they are on a slower intermittent level. They kind of exceed the starting point, wipe further down, then come back up again to the starting point. It's annoying me! Just wondering if this is normal? Or, is it a worn wiper motor? Or, can I simply adjust them? Thanks for all your time and help!

Todd