Sometimes the car moves when I put it in drive and push the gas, and sometimes it just sits there with the engine revving, almost as if I am in neutral. It's hard to tell when it is going to happen.
With the car warm parking brake set and in park (automatic) neutral (manual shift) while on level ground check the transmission fluid level, it should be within the hashmarks. If it's low this could be your problem, the amount of fluid it takes to get from the low mark to the high mark is only a half quart so be careful not to overfill. If the level is at the correct level and the problem persists it might be an internal transmission problem that would need to be diagnosed by a certified transmission mechanic.
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