The jar file is just a container what you imorted were rules and possibly some data structures.  Deleting a reference to the jar file will not help the rules have been imported into the config database.  Did you import them into an exsisting ruleset?  If they were imported into thier own ruleset then you can just delete the entire ruleset. Otherwise your best bet would be to search for rules changed on the date you imported the jar and delete them that way.

Let me know if this helps,

Cecil Howell

Senior Instructor, Pega Academy