Hey, when i am driving down the street and my foot is still on the accelerator my car will jerk back and fourth. what happens is say i am at a normal rpm rate of 2.5 suddenly the rotation speed will drop to a 2.0 or so and then increase back to the original rate. this causes my car to jerk back and fourth as if i don't know how to drive stick. at first i thougth maybe my spark plugs have gone bad but after replacing them the problem is still there. i have had a mechanic check my fuel pump and that was alright too. is tehre anything else i should look any advice would be much apprecaited.