When your fuel injector is bad the most common symptoms of a bad fuel injector will be rough engine idle, hard starting, bucking and surging of the engine while under load,loss in fuel mileage and an engine that doesn't reach full RPM.
Also if your fuel injector is cracked or broke you may notice a gasoline smell coming from the engine bay which could be a fuel leak and it needs to be checked out because having a fuel leak from a fuel injector or any other part of the engine could lead to a vehicle fire so get it checked out especially if you smell gasoline.