I have a 1994 Camaro with a 3.4 Liter V6. 2 weeks ago it started missing and all the gauges started junping around. I checked the battery thinking the connections might be loose but they were fine. On the way home did it again and when I shut it off , it wouldn't start. Had a code for the front crank sensor so replaced it. Still wouldn't start. Found out the ignition switch was bad so I replaced it. Now it will start if you hold the throttle open and keep it above 1500rpms. After about 5 minutes it will idle fine and run great but if I shut it off it won't start or it backfires. It also had codes for a tps and a coolant sensor so I replaced them . Still the same. I then replaced the map sensor and the cam sensor. I also checked all the wires from the sensors to the computer. I have even tried a new computer with no luck. I have no idea what to do next. Any help would be greatly appreciated.
Don't know much about these cars, but a friend of mine was having similar issues. His tach was even jumping around. Turned out the alternator was not charging correctly & was somehow pulling power. New alternator fixed the issue.