Charging system info non mopar

Sounds like a bad battery. Just because a battery has 12 volts it doesn't mean it's good. It may have a weak or partially shorted cell. Still measures 12 volts until you put a load on it then it goes away. While this may allow the starter to work, it's sucking all the juice out of the battery and there's not enough left to supply the ignition system properly. I assume this is a computer controlled fuel injected engine right? If computers don't get the required voltage they can do funny things.