I have a 94 camaro z28. I got it with a 120,000 miles and missing terribly. After fixing the miss I disovered a spun bearing. I decided to replace then engine. After I got the new engine in it started up fine and ran great. Started it up three times running fine but it stalled the 3rd time after running for about 15 minutes. Ever since then it doesn't want to start and when it does start it'll run really rough for about 5 seconds then stall out. I've checked all the sensors and they're all connected. Timing was set and engine was primed before starting. Any suggestions? I'm out of ideas.