i went over a pot-hole driving one day, and after that, my speedometer just jumps all around and hardly works, ive noticed when it is bounceing all around the transmission shifts up and down and up and down ( automatic) like it cant decide where it wants to stay, when it does this at high speed the engine back fires, i am limited to drive in city only not on highway, i need help i dont know what to do, and am very frustrated.

 

Get under the car and check the speedo and vss sensor connections to the transmission. It might me a loose or broken connection.


I may be wrong, but the VSS sends data to the ECM which in turn adjusts fuel pressure and possibly your shift points.

The speedo connection is self explanatory.