Fuel and Air Intake
Fuel injection consists of a throttle body to control airflow, the fuel injectors, various engine sensors, an electric fuel pump and a fuel filter. The system is controlled by the car's powertrain control module (PCM), which makes all decisions for controlling the injection system. Most early fuel injection systems used a throttle-body design, where one or more injectors were mounted on a throttle body, resembling a carburetor. Use of the throttle body system faded away gradually as multi-port fuel injection became more prevalent. Multi-port uses a separate fuel injector for each cylinder, located near each cylinder's intake valve port. Virtually all engines now use multi-port injection.
Fuel injection delivers fuel to the engine in exactly the right amount for all engine-operating conditions. Not only does the system provide better control for fuel economy, performance and emissions, it also does away with many of the maintenance requirements of a carburetor.
On cars with fuel injection, some carmakers don't recommend replacing the filter at all during the first 170,000 kilometres of "normal" driving. Since "normal" usually constitutes severe driving because of less than normal conditions, it's best to replace the filter every two years or 40,000 kilometres. A contaminated filter can restrict fuel flow from your car's electric fuel pump, eventually taking a toll on its life. Frequent filter replacements remove all doubt about whether the filter may cause other problems down the road. On 1996 and newer vehicles, your car's fuel injection system is integrated with a second-generation onboard diagnostic system, known as OBDII. The PCM stores a Diagnostic Trouble Code (DTC) when it detects a problem in one of the monitored circuits. A professional technician can access this information using a scan tool connected to the vehicle's Data Link Connector (DLC). Although many DTCs are sensor-related, it does not necessarily indicate a faulty sensor. There may be problems in that sensor's circuit, or there may be several interrelated problems. Areas of the country with an emissions testing program are placing added value on OBDII checks, where this technology may be used in place of tailpipe testing. The system also alerts you with a Malfunction Indicator Lamp (MIL), indicating that the system has detected a problem, which could cause excessive emissions. This light is usually labelled SERVICE ENGINE SOON or CHECK ENGINE. If the light appears, you should have its cause investigated by a professional technician at your earliest opportunity. If the light flashes, the condition is more severe and must be checked out immediately to prevent damage to the catalytic converter.