Most likely going down hill, the faster the wheels go, the higher the RPM will increase, for this to increase the vehicle either must be going downhill with no brakes applied or the throttle(acceleration) has been depressed.
A lot of possible causes, I recommend a careful investigation.
For starters change the fuel filter
Your alternator is probably not keeping the battery charged while the car is running. You need a new alternator!!
Cylinder miss.
will the transmission causes my 1999 ford expedition to bog down & sputter when accelerating the 4.6liter engine.
you need to get new spark plug leads
I means you need to get a new car those are outdated
This depends on how you define your axes. Let's assume they're defined as normal (being positive is accelerating, negative is breaking, and for velocity positive is driving forward, negative is driving in reverse). Then of course, you are speeding up. This simply means the train was in reverse, but it's accelerating in the positive direction now.
A damaged catalytic converter could cause that.
Press the brakes or down shift
the wineing is probably the fuel injecters because that is what was wrong with my dads truck.
A warped rotor can cause a vehicle to have an intermediate hop in one of the wheels. Check to see if the brakes of the car need to be serviced.