NOT SURE?

NAME RICH I HAVE 1997 JEEP CHEROKEE SPORT IT JUST SHUTS DOWN WHILE DRIVING. ITS USED TO DO IT ONCE IN A WHILE. I'D LEAVE MAINE GO TO NEW HAMPSHIRE IT DIE 75 MILE OR SO PULL OVER LET SIT 45 TO HOUR DRIVE A WAY. FEW MONTHS LATER DO IT AGAIN. THEN EVERY 23 MILES IT DO IT. PULL OVER LET SIT START UP AND GO. STAY OFF HIGHWAY RUNS GREAT. THEN HAPPEN FEW MONTHS BACK LESS THEN 15 MILE. LET SIT AGAIN NEXT DAY RAN GREAT TILL TODAY 1-27-11 IN CITY.I'VE BEEN TO 3 DIFFERENT PLACES AND HAD 3 DIAGNOSTIC'S DONE. SENSE 2010 THERE HAS NEVER BEEN A CHECK ENGINE LIGHT COME ON?SO FAR THIS IS WHAT I DID. REPLACED SPARK PLUGS-CATALYTIC CONVERTER-MUFFLE-OXYGEN SENSOR-R&R CRANK SENSOR-THROTTLE POSITION SENSOR-AUTO SHUT DOWN RELAY-IDLE AIR CONTROL-MAP SENSOR-RESET BASIC IDLE-MANIFOLD AIR TEMPERATURE-K&N AIR FILTER. SO HAD TOWED LESS THEN 15 MILES TODAY GOT HOME STARTED IT UP IDLED FINE BUT NOT GONE FOR A RIDE IT COULD HAPPEN ANYTIME NOW? I REALLY NEED HELP AND DON'T HAVE ALOT OF MONEY. ANY HELP WOULD BE GREAT THANK YOU richsasseville@yahoo. Com