I have a 1993 Geo Tracker ( 2 door, 4wd, 5 speed) and it starts up fine and will run good for a minute then it starts coughing and misfiring. If you turn it off and start it again its fine for another minute. Then it does it again. It has a brand new fuel pump, new plugs, fresh oil change and a clean distributior. Any ideas what it could be? Ive heard it could be an o2?