I hear a loud noise coming from the engine and the car won't go over 20 MPH.
With the speed limitation and the loud noise, I recommend not driving the vehicle until it has been diagnosed and repaired. It sounds like the vehicle is either in limp mode or a mechanical failure has stopped the vehicle from moving properly. A qualified technician, like one from YourMechanic, will be able to diagnose your acceleration issue and perform any repairs that are required.
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