While driving, the car stops accelerating and loses speed. Doesn't go over 15mph

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Whan driving, if the rpm goes over about 2 1/2 (sometimes just at 2) the car stops accelerating and won't go over 15 mph, the rpms just keep going up. I usually have to pull over and turn off the car to let it cool down (i live in south florida). Sometimes that doesn't even do the trick and i have to get to point b at turtle speeds. I know the ac is messed up and not cooling, could that be related? When the problem occurs i can hear a hollow whirring sound coming from the car and most recently, a rattle. My dad changed one of the sensors on the pistons and I'm back to square one. Please help, I'm about to junk this damn car.