Ok, the car has done this since i got it, but sometimes i like to turn it to ACC and leave the radio on when im cleaning the inside of it out. The first time i do it , it will stay, but after that it just goes back to the off position instantly, it wont stay turned back. So what needs to be replaced, the lock? And how much?

 

The ignition switch may be slightly out of adjustment. Look at the ignition switch R&R on my Tech Page and you can see how you can get to it to try adjustment.