Chevrolet: 1988 Chevy Celebrity, chevy celebrity, spark coil

Question
We have a 1988 Chevy Celebrity.  When stopped at a light the car will die.  It turns right back over but if you try to move forward it will die again. You can restart it all day it will turn over every time.  It will idle just fine, but will die again if you try to move. After sitting for 15- 20 min it will drive again.  Someone told us to check and see if removing the gas cap would relieve a possible vapor lock.  That doesn't work and it doesn't seem to have alot of pressure behind the cap.  We have replaced the fuel pump, thermostat and done a complete tune-up.  Please advice.  Thanks

Answer
You should have the ignition spark/coil pack checked out. Could be weak spark, then again it could be either a sensor or to. It would best best to have the vehicle scanned on a garage computer, this way it will give the mechanic a trouble code, and he will be able to tell for sure what the problem is. I can give you a quess, but its hard to tell for sure. Ty..