When on the highway (and this only happens on the highway), my car starts jerking as if it wants to go faster. On its own, it will jump from 2,000 rpm to 4,000 rpm and this goes back and forth. I have to floor the accelerator before it will properly run. What is causing this?
When an engines rotation speed increases the speed should increase. If it isn’t, then there is likely an issue with the torque converter (an automatic transmissions clutch). If the speed is increasing, it could be an issue with the cruise control. Is it possible the cruise control was turned on by accident? It is also possible the vehicle has a vacuum leak as that would cause RPM fluctuations as well. A certified professional from YourMechanic can inspect the jerking issue and pinpoint the appropriate repairs to have this corrected.