After 1990, cars were built with fuel injection systems rather than carburetors because fuel injectors offer better efficiency and performance in delivering fuel to the engine. In this system, when you step on the gas pedal, the Engine Control Unit (ECU) of your car calculates what the air-to-fuel ratio should be and signals to the fuel injectors. In response, the fuel injectors send a high-pressure spray of fuel to the cylinder, which then powers the engine and makes the car move at the appropriate speed.