I have a 1987 Gmc Jimmy 5.7 350 v8 full size automatic. everything was good until about 20 minutes into my drive when i went to take off from a red light the truck began to cut out. so i babied it and got it to go. once it gets it in second gear it runs fine. and doesnt cut out. i tried using STP fuel injecter cleaner but it didnt help. HELP PLEASE!

 

Might need a tranny flush. If one gear is not working properly in an automatic, it makes me believe that the passages in your tranny might be crudded up and need cleaning.

 

have you checked your fuel filter or fuel pump?

 

It could be the fuel delivery ( pump,filter pressure regulater) or even an ignition problem check plugs, wires, etc...

 

have you done tune-ups lately? it could be that your ride needs some tune-up. it is also good to check some tune-up parts like spark plugs, gmc spark plug wire, fuel filters, pump, etc.. to see if there's a need for replacement.. good luck! keep us posted what other things did you notice upon checking those parts..