1998 Jeep Cherokee spudder, missing

My jeep spudders and or misses when driving or idling, had wires cap rotor done been to 3 shops and problem still not fixed. I am a single mom and just want to know what it is, not be sucked dry of money, the last place that took needless money out of a already poor mom says its a crankshaft position sensor. Is this a right diaognos, its been on the machine more times than I care to think of and it doesnt seem to detect anything major. Help me please. Thanks much, mojo