when i went to go start my car earlier the tach fell down to zero the engine shook but it hopped back up to idle. i turned my car on and off a few times and it did it everytime and it did turn off the one time. I did have a service engine soon light before all this happened so i disconnected my battery and the light went away but now this is occurring. the car runs and drives fine. any ideas?

 

Crank Position Sensor / Camshaft Position Sensors