I have a 90 century with the 3.3L and this problem just started 2 weeks ago. I haven't dug into this problem, as I'm still doing some research on it. But see if this is the same problem as you... On start up after the engine has been warmed up, I tap the gas pedal while in PARK and I notice the engine hesitates, shutters, and then stalls. Next time I start the car, I put the gas pedal to the floor only to have the engine shutter and stalls once again. On the thrid or fouth try I hit the gas a little bit to see what the engine is doing and like MAGIC it revs like normal and everything is fine and I drive away.