Yes, faulty glow plugs can cause a car to smoke. Glow plugs are a critical component of a diesel engine's ignition system. They heat the air inside the combustion chamber to help ignite the fuel and start the engine. If the glow plugs are not working correctly, the engine may not start easily, or the fuel may not be burned correctly, leading to incomplete combustion and the release of unburned fuel as black smoke from the exhaust. If you suspect that your glow plugs may be faulty, it is essential to have them inspected and replaced if necessary to prevent further issues.