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Q: Car is showing random misfire code po300

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I accidentally let go of clutch and gas in 1st gear causing car to turn off and jump foward, after i turned car back on it started shaking extremely bad, check engine light came on and now idles rough at 100 rpms normally would be at 1000 rpms. While driving it home like that i noticed that normally i would change gears at 3500 to 4000 rpms instead it was needing to change at 2000 rpms no matter what gear i was in. Ive changed the spark plugs, spark wires, coil pack but i dont want to keep wasting money on random stuff im hoping someone has had this happen to them i need help please

My car has 123000 miles.
My car has a manual transmission. Here is video link of my car.
https://m.youtube.com/watch?v=BrA6CY3R6uU&feature=em-upload_owner

The only sensor that will cause the RPM gauge to read incorrectly and cause a rough running engine is the crankshaft position sensor, or its wiring and connector. Try and disconnect the crankshaft sensor connector located above the oil filter on the side of the engine block. Look for any damage to the sensor or the connection. If you do not see any damage then the sensor should be tested or replaced and the codes cleared to see if it corrects the problem for you.

If you need assistance, a certified mobile mechanic can come to your home or office to inspect your vehicle’s issues and provide any necessary repairs.

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