Fuel injectors have taken the place of carburetors on nearly all modern cars, as they improve fuel economy, emissions and engine performance. When the injectors spray gasoline into the combustion chamber of the vehicle, their design helps to break apart the fuel into a fine mist that allows for an even and efficient burn. If they become clogged or are otherwise not working correctly, this can lead to a number of mechanical problems. A fuel mixture that is too lean (more air than gas) can cause an engine to misfire or even stop running entirely in extreme cases.
Leaky injectors can flood the engine as well. Excess fuel in the combustion chambers can pool up. When the engine is shut off, the gas will evaporate, settle and cause damage to the engine upon restarting it. Preignition, while rare, can result from leaky injectors as well. This occurs when the fuel mixture ignites before the spark plug fires. This may cause the engine to overheat and can damage the pistons as well.
If the engine is hesitating or stalling, there is reduced power, emissions are increasing, mileage has dropped drastically or the car won't even start, you could be looking at failing or clogged fuel injectors. If the injectors are clogged, you can clean them, which should get the fuel system back in working order. Heavily soiled injectors will likely need to be removed for cleaning, but you can try to run a cleaning product through the system first to see if that does the trick.
To do this, you will need fuel injector cleaner, which is designed to remove any deposit buildup that may be clogging the system. This goes for the fuel injectors as well as the combustion chambers and the valves. An injector cleaning kit will also be necessary for this project. The kit should come with specific instructions, but here are the basics.
To start, you'll need to either install a U-tube or disable the fuel pump and plug the fuel return line to ensure no fuel gets into the engine while you're cleaning the injectors. Next, hook up the cleaning kit and pump the pressurized cleaner through the engine while it is running. When you're done, turn off the engine and reconnect the fuel lines and pump. After the process is complete, restart the car to see if the cleaning process has improved the engine operation. If there's no noticeable change, repeat the process once more.
After the second attempt doesn't change the condition of the engine, you'll probably need to remove the injectors and clean them that way.