Engine is revving when still

When I am parked or have my foot on the brake, my car will rev, sometimes up to 3 or 4 on the dial. The original error code was the Mass Airflow Sensor. We changed that yesterday, and it is still revving and it shut off twice within ten minutes in a parking lot. It shut off without making a sound. We took it to get the code checked and it still says Mass Airflow Sensor.