Our 98 Taurus has a problem that so far four mechanics have been unable to fix. When you are driving all of a sudden it just wont go. The engine doesnt die it just wont move even with the gas peddle to the floor. The tach doesnt rev up or anything so we think it is maybe fuel pump issue. the mechanics have done the following changed a o2 sensor (dont know which one or how many) changed the thermostat cleaned the egr valve and replaced some kind of temperature sensor. any help would be appreciated the car has been in the family since bought new and we would really like to get it fixed.