Although the carburetor was an important part of the vehicle decades ago, the fact is that almost all modern cars made in the past 20 years do not have one, instead opting for fuel injection systems. While carburetors are no longer popular and most amateur mechanics will never need to know anything about them, it can be useful in understanding how they work in order to get a better idea of what your fuel injection system does.
Simply put, both carburetors and fuel injectors are responsible for controlling the mixture of air and fuel that goes to an engine. The modern combustion engine needs both of these critical components in order to run, but ensuring the engine gets the right mix is a difficult task.
Given how complex engines are, it needs a different mixture at different times, depending on the temperature, acceleration and other critical factors. Carburetors are mechanical devices, meaning that they can only react to these changes by measuring conditions and instituting changes. Old carburetors did this by circuits - the air and fuel would essentially take different routes to the engine on each circuit, resulting in different mixtures.
A good example of this is the choke, which was used in colder temperatures. Cold air condenses fuel, meaning that the carburetor needs to get more fuel in order to start the engine properly. This is one of the reasons why many people had trouble starting their cars in the winter during the seventies and eighties. Ideally, the choke is supposed to create a vacuum that causes more fuel to get sucked into the engine.
Modern fuel injectors ignore many of these problems because they work based on electronic software. The software can instantly detect things like temperature changes and how the car is traveling in order to get the correct mixture of oxygen and fuel. These systems can also deliver the fuel directly to each cylinder, increasing power and performance. Overall, this system ensures that fuel is not wasted, which helped automakers increase the fuel economy of their vehicles. It also cuts down on the amount of emissions that a car generates, which became especially important as the government began cracking down.
Of course, this system only works if its measuring everything correctly. This is why something like a faulty oxygen sensor can be so damaging - it can quickly cost a driver a ton of money in fuel costs. It might behoove drivers to be proactive about their oxygen sensors, as the Department of Energy claims that a broken one can decrease fuel economy by up to 40 percent.