I've got a 90 S10 Blazer that will start run for 5 to 10 seconds and die. It will finally start and stay running as long as I don't shut it off, if I do everything starts all over and it can take 5 to 10 tries to get it going. So far I've changed , cap, rotor, plugs, fuel pump, ignition modular, fuel reg, and the map sensor, anyone else have this problem and what was the cure? TIA