1994 Ford Thunderbird SRS 4.6 V-8

MY CAR WAS RUNNING FINE UNTIL 2 WEEKS AGO. IT BEGAN SHUTTING OFF IMMEDIATELY AFTER I STARTED IT. AT FIRST I THOUGHT IT WAS A FUEL PROBLEM, POSSIBLY FUEL PUMP OR FILTER, BUT AFTER I CHANGED THE SPARK PLUGS THE CAR PERFORMED GREAT UNTIL THE NEXT DAY. THE SAME PROBLEM RE-SURFACED; IT STARTS EVERYTIME I CRANK IT BUT SHUTS OFF AFTER A FEW SECONDS. I HAVE TO KEEP THE ENGINE REVED UP JUST TO KEEP IT GOING AND SOMETIMES THAT DOES'T WORK. THE FEW TIMES I DID GET IT TO RUN RIGHT I WOULD BE AT A STOP LIGHT, THEN ALL OF A SUDDEN I WOULD LOSE POWER, BY PUMPING THE GAS PEDDLE IT WOULD GO BUT WHEN I SLOW DOWN THE CAR SHUTS OFF, THEN I HAVE TO START, PUT IN GEAR FAST BEFORE IT TURNS OFF. PLEASE TELL ME MY PROBLEM IS SIMPLE?