a/c rough idle

I have 04 tahoe, I start my tahoe and instantly everything sounds different. The idle is really low, my exhaust isn't loud like usual. And it feels like it's running out of gas.,i let it idle for awhile and it goes up and down. If I rev the motor, my oil gauge goes up and when released it...

went out and battery is dead. hooked up jumper cables and cooling fans come on as soon as i connect clamps. been sitting for 24 hrs. drive about 26 miles notice with a/c on idles rough and almost dies.(runs great with a/c off). next day battery dead again. new battery. as soon as i hookup...