Lat fall, engine started losing rpm at crusing speed. It would die off...then surge...then die and sometimes reutrn to normal for a period, or completely conk out. The fuel lines and injectors were cleaned, bulb replaced, plugs replaced, O2 sensor and fuel filter replaced and problem went away...for 45 hours...now it's back again. WE have cleaned fuel lines, replaced fuel filter and plugs, tested fuel pressure and inspected fuel tanks..no idications of problems anywhere and no help for motor problem. After motor cools off...it starts again fine and runs anywhere from ten minutes to an hour before problem reappears. Question: what should we try next... and if you think it could be either the 02 sensor or injectors again...what would cause an engine to run fine for 800 hours then this identical problem so soon? Gas is bought from same location and ring free added meticulously, plugs changed every year and every 40-50 hours.
