Re: 2004 3.0 DOHC Starting Problem
Probably the alternator.
If you have a voltmeter check the battery voltage before starting the car and after is has sat at least 4 hours. Should be 12.4 or so.
Then start the car, turn on as many electrical devices as possible; AC, lights, blower fan on high, then rev the engine to 1500 rpm. Voltage should be +13.7V.