The EFI or electronic fuel injection system on most modern cars comes with several vital sensors that can affect how the engine runs if they are not working right. The sensors and the engine management computer have to work together to tune the fuel/air mix properly, so if even one part is not working, the entire system can malfunction.
ECU and Sensor Intergration
All fuel-injected engines need to have a system that controls the fuel and air mix going into the engine. The electronic control unit or ECU is the brain that holds all the fuel maps and calculates the required mix based on the sensors in the system.
EFI (electronic fuel injection) systems rely heavily on the sensors' information, so if they are not communicating correctly with the ECU, the entire system can fail to operate correctly. Some of the most common failure points include the O2 (oxygen) sensors in the exhaust, the MAP (manifold absolute pressure) sensor in the manifold the TPS (throttle position) sensor on the throttle body.
The O2 sensors are located in the exhaust system just downstream from the manifolds. The role these sensors play in the EFI system is to report the percentage of oxygen in the gases coming out of the engine.
These numbers are used to calculate the fuel/air ratio that is going into the engine. The air and exhaust gases can let the ECU know if the system is burning fuel efficiently or if the EFI is running too rich or too lean. A bad O2 sensor can have a significant effect on the car's driveability and should be replaced.
MAP and TPS Sensors
The manifold absolute pressure sensor reads the vacuum inside the intake manifold and tells the ECU how much load is on the engine. As the load increases, the MAP sensor can report vacuum conditions that tell the ECU the engine needs more fuel and air so the EFI fuel map can be adjusted, and the engine will produce more power.
Simultaneously, the throttle position sensor or TPS is telling the ECU how much air is coming in through the throttle body so that EFI can adjust the fuel at the injectors to create the perfect mix of air and fuel inside the engine. If the sensors are off even a little, the engine efficiency will drop, and the engine will often not run properly.
In most cases, they are not repairs you can make at home because the reading and adjustments to the EFI require special software and a computer system that can decipher the codes. Taking your car to a repair shop with the equipment for these repairs is the best solution and can save a lot of time trying to determine what part of the system is failing.
Contact a local auto parts store or a mechanic if you have more questions about electronic fuel injection systems.