A throttle cable is a cable that connects the gas pedal to the engine's throttle valve. When you press the gas pedal, it pulls the throttle cable and opens the throttle valve, which allows air and fuel to flow into the engine. Throttle cables can wear out over time due to normal use and exposure to heat and corrosion. Symptoms of a worn-out throttle cable include a stiff or unresponsive gas pedal, difficulty accelerating, and a decrease in fuel efficiency. If you notice any of these signs or if your vehicle fails to pass an emissions test, it may be time to replace the throttle cable.