I have a 88 GTA I put a brand new 350 Vortec motor from ATK into it have about 12000 miles on it. I was driving and the car started to backfire and died out. The car stalls from time to time in stop and go driving. In traffic if I got stuck at a light id go to accelerate and it would shut off sometimes giving me a hassle to start up. I would have to nail the gas and rev the rpms up then throw it into drive and go. It has spark at the coil the coil is brand new I did a probe light test. I put all new wires and plugs w motor I even replaced the cap and rotor again after it broke down because I figured it had to be that if no spark at wires but at coil. Stumped. Motor turns by hand. Pressure at the fuel rail. No start. Did 3 different spark tests at wire one with screwdriver, in line tester from harbor freight, and the one that goes to negative battery cable and wire. Anyone? Thanks

 

Cap is sitting correctly? Rotor turning? Spark coming from coil on the coil wire?