I have a 1996 Buick Century. I took my car to a mechanic because when ever I would accelerate the gas pedal while on park it would go Vrooom! Vrooom! Vrooom!!! I actually would push the gas pedal all the way down and hold for about 3 to 4 seconds and the engine would go VROOOM! VROOOM!!!! The mechanic said it was normal he said that all cars do that, it is so that you don't damage your engine. I guess it's some kind of sensor that kicks in, I don't know. Is he right? I'm still kind of confuse I've never notice that in any family or friends car.