When i start it up it runs, and than it dies about 50 feet later. i wait for awhile and than it starts back up, and does the samething. i tested the alternator and it was good. and sugestions what it could be?

Sounds like your fuel pump might be giving you a hard time I would start there on testing

change the fuel pump relay.

check your AC compressor

This engine is electronically controlled so the first thing that must be done here is to have the systems control computer tested for fault codes and then do the proper diagnostics based on those codes.

if the key is off and the fuel pump still running then the fuel shut off switch and or the fuel pump is bad and needs replaced. More than likely the fuel pump might need to be replaced. (my 86 5.0 did the samething)

check fuse pump

replace the IDLE AIR CONTROL , samething happen to me ...i clean mine at first and it worked for awhile but had to replace it after a couple of months.its on the back side of the throttle body helled on by 2 small bolts

check the crankshaft position sensor

Ignition coil or Ignition control module I would look towards the ignition control module.I had a 91 cavelier do the samething exact same and i tried everything to try and fix it,it turned out that it was the ignition control module. There will be 2 coils mounted onto that plate.It ran good till it warmed up,once warmed up it would stall and spitt and sputter,if left for awhile would start up and go good untill it warmed back up.Once the module would get warm it would quit working untill it cooled down

You can check for spark if there is none then check for power to the coil if that checks out the replace ignition module .