2001 Nissan Sentra GXE 1.8 runs fine until engine is warmed up.

replaced the crankshaft position sensor
test drove Fine. The next day I drive it to
town and as I'm riding I ease up on the gas
pedal and it starts kicking back and
sputtering. It was kind of like hiccups for a
car. pressed on the gas and gave it just a
few more rpms  and it stopped hiccuping.
However stopped at a light rpms dropped
sputtered at 500 and shut off When
stopping. when slowing down had to play
with the rpms and break just to keep from
stalling out.