Kathy, I need more info (year, make and model of your car) but will give you my answer as it relates to most cars. Most cars today use wireless ignition so coil wires are a thing of the past. Traditionally when coil wires go bad it is caused by corrosion (dirt and heat) that results in loss of power, hard starting and hesitation under power. You can remove the old one and inspect it for corrosion at the terminal ends but to be sure replace with a new one or one that is known good. I hope that helps.