It has been a frustrating weekend of work on the Jeep. It's a 1990 Cherokee with 424 6 cyl MFI auto tranny. It is a pain to get to start up cold or hot. Starter cranks fine but motor won't turn over and idle without a fight. Once running it has a "dead spot" in the gas pedal just as it is depressed that will cause it to stall out. I did a complete tune up new battery, plugs, wires, distributor, filters. Is it a sensor gone bad? What needs to be replaced to correct this?