Last month my car started revving up randomly while in park. Once I put the car in drive it would pull forward on it's own speeding up to 40 mph in the worst case. It ran so rough pulling and stopping the only thing I could do was put it in park until the RPMs came back down to a normal rate. From that point on, every time I started the car when it wasn't warmed up this would happen. It used to only take about a minute for the RPMs to settle and the car to run fine. Now it takes about 5 minutes of warming up, settling and then drives very poorly in first and second gear.

One month later the car hesitates when given gas, begins to "rumble" slowing down, and feels like it will stall out as the cars RPMs approach 0. I took the car to a mechanic and they found no problem. They said the RPMs were lower than normal on idle. I read online that there could be a vacuum hose leak causing air to be forced into the engine causing the issue but that wasn't detected by the mechanic.