2000 Ford Ranger engine problem

I have a 3.0 flex fuel 2000 ranger every 4 months the engine will quit running put on a new fuel filter its fine for another 4 months take the fuel filter apart and theres no dirt or junk in it. Then I wash the truck through a drive through car wash and every time you slow down for a red light it dies put it in n start it up and go to the next light where it does it again I have been told transmission converter is not locking and unlocking and I have been told fuel pump but the fuel pump pessure is 55 where it should be for flex fuel system. Ford dealer hooked up computer and can find nothing. Thanks for your time.