The throttle position sensor is on the side of the throttle body, it's a little black box with a 3 contact connector on it. One is ground(the middle one) and the outer two pins are full throttle and idle contacts. Only the idle contacts are used on sticks, automatics use idle and full throttle contacts. There are two screws on the switch so you can adjust it, they rarely go bad. With an ohmmeter, rotate the switch until the idle contact is closed with the throttle closed. It should open when you just barely push the gas pedal, telling the computer that the engine isn't idling anymore. You can't adjust the full throttle contacts separately, so you're stuck with however they work if you have an automatic. If your car lurches a little while coasting in gear towards a red light, it may be that the TPS is not quite right and the computer is switching from idle to running. This can make your car lurch a little because the fuel is shut off when you are coasting in gear to save gas. The switch is opening and closing, turning the fuel on and off. To replace the switch, simply remove the two screws, unplug it, and replace it with the new one.