Throttle cables link your accelerator pedal to the engine, and if they stretch, break or bind, you're going to have problems getting from "A" to "B." They're not difficult to replace, and it only takes a little bit of time to do so.
Disconnect the throttle cable on the engine. Generally, this is held in place with a clip which can be undone with a flathead screwdriver. Sometimes there is a mount which holds it in place, and then you'll need to use a socket.
Disconnect the throttle cable from the bracket that holds it to the intake manifold. These usually are pressed into place, so if you push in the tabs, it will come out easily.
Push the throttle cable through the firewall. On some vehicles, it's just a rubber grommet. It may also be clipped in similarly to the intake manifold bracket.
Disconnect the cable from the accelerator pedal. Usually there is a slotted hole on the pedal which you can just lift the cable from, but sometimes it's secured by a bolted bracket, in which case you'll need to unbolt the bracket.
Installing the new cable is done in the reverse order of removal. Be sure to use a quality throttle cable to replace the stock model.
