OK. 1996 Ford Explorer replaced computer, water pump, ETC, plugs, plug wires, and starter. Put in head/lock sealant in coolant -new coolant. Hard to start once started will start as long as motor is warm once motor cools off hard to start ,also backfires while trying to start. If has set for a while white steam out of exhaust. Is this a blown head or head gasket? About to take to junk yard very frustrated!! HELP PLEASE ANY OTHER IDEAS?