Fixing a LaserJet 4 printing pages after a print job

Separator pages?
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=110&prodSeriesId=25487&prodTypeId=18972&prodSeriesId=25487&objectID=bpl01375

Or, try printing a demo page and see if it does it there

Or, Select LaserJet4 Plus driver and see if that helps.
Or, try setting lines to 60 and nothing more. It’s a page printer, if there are 64 lines or more, it will put things on a second (blank) page.

Also, try turning of “Bi-directional Printing” in the printer properties.

If not, the printer just may be busted.