If your originals have black streaks or appear dirty after they have been through the automatic document feeder, clean the automatic document feeder rollers.
It takes approximately 20 seconds to clean the rollers of the automatic document feeder.
Make sure the list of scheduled jobs is empty.
Make sure you have clean A4 / LTR plain paper (60 - 80 g/m² / 16 lb bond - 20 lb bond).