I have a ‘96 Altima GXE with the 4 speed automatic with overdrive. I’ve owned it for several years and it’s always had this problem, but it’s becoming worse. Whenever the car is in reverse, and only reverse, the car accelerates on its own and becomes extremely hard to brake and stop it. It floors it and goes and full force on the brakes hardly work. It doesn’t stop until I put it back in Park. I checked the tranny fluid, and all other gears work fine. I told a mechanic and they replaced the idler control valve and throttle body, and it didn’t fix the problem. They told me they don’t know what else it could be.