Today I drive it after sitting for about a week. Starts normal let idle for a little while, drove it. Everything was hunky dory until it happened. After getting to normal temperature, the voltmeter I have starts dropping. And the car starts idling roughly like it wants to shut off. According to the meter it will stay around 13 or 14 volts but like I said once it starts getting hot(the engine) or whatever the volts drop and goes back up if its not hot enough yet. But once it's hot it will idle roughly and just shut off. Any ideas?