I have a 2007 Pontiac Grand Prix that won't start.
My car has been in the repair shop starting the 3 mo. they have replaced the fuel pump
the plugs, coils, and key switch. If it is inside it will start but if left outside it won't.
A very weak battery can be affected by temperature. If its not starting because the battery is weak, I'd say its time for a new one. Of course if it turns over fine but won't fire, then that rules out the battery.
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