Can cars start with a bad spark plug?
Can I start my car with a bad spark plug? If it’s just one bad plug, you probably can. One bad spark plug will keep the fuel from consistently igniting in that cylinder, leading to a rough idle and reduced engine power. This is less of a problem in engines that use two spark plugs per cylinder, since the working plug helps ignite the fuel. Multiple bad plugs will keep the fuel in the cylinders from firing consistently. While you might get the engine to start, it won’t be able to idle.