A bad battery can cause a cylinder misfire, meaning that one of the cylinders in the engine is not firing correctly. This is because a weak or dead battery will not be able to deliver enough power to the spark plugs, which are responsible for igniting the fuel-air mixture in each cylinder. When this happens, some of the cylinders will fail to ignite properly and cause an incomplete combustion cycle. This can lead to decreased performance as well as increased emissions from your vehicle. A diagnostic scan should be performed if you suspect there may be an issue with your battery causing a misfire so that any underlying issues can be addressed before further damage occurs. Additionally, always ensure that your battery has adequate voltage prior to driving; otherwise you risk having other components suffer due to lack of power supply from your car's electrical system.