Jurking Traney

The engine is idling too fast. The most common cause is a vacuum leak. Check the vacuum hoses around the top of the engine and especially the larger one that goes to the power brake booster. Often you will be able to hear the hissing.

Intake manifold gaskets can cause the same problem. One way to locate that leak is to use a spray bottle to spray water around the gaskets and hoses while the engine is still cold. If you spray the leak, you'll see the water get sucked in and the engine will slow down for a few seconds.

If nothing shows up, have a mechanic check the throttle linkage to be sure it is returning to idle properly. An engine that won't slow down can lead to loss of control and a crash, and should not be ignored. Don't overlook a gas pedal that is stuck under the floor mat.

"it makes a hard jurking noiseand I have t hold the break pedal down hard so it dosen't go backwards fast"

If the car is moving too fast without you pressing the gas pedal, it's idling too fast. That is very hard on the transmission and drive axles.

You don't have a carburetor and the idle speed is computer-controlled. It didn't suddenly adjust itself too high. If the idle speed is too high, check for a vacuum leak.