Car won't stay on after replacing crank shaft position sensor??

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My car would turn over but would not start. I tried about 5 times and it finally started with the check engine light on. It also started perfectly fine two times after that with the check engine light disappearing. I took it to AutoZone to run OBD 2 and the error code was a faulty crankshaft position sensor. I replaced the crank shaft position sensor, only removing the engine cover and the mass air flow sensor for easier access to remove the craft shank position sensor. Now when I start my car it turns on with no check engine light but the RPM's jump to about 2000 and then drop to either 500 or below and then it dies. I am able to keep the engine running if I keep the RPM's high by applying gas. Could it be the Mass Air Flow sensor or something worse?