A Fuel Filter is designed to restrict impurities from getting into the fuel injectors. Over time the fuel filter can become to restrictive and cause a lower fuel pressure which leads to poor fuel mileage and poor performance. The fuel filter should be replaced every 30,000 miles. A clogged fuel filter can lower fuel pressure 3 to 5 psi. And in some cases this can make the difference for an engine to start or not. If you need instructions on replacing your fuel filter we recommend this Online auto repair manual for detailed instructions and how to photos.

Fuel Injector

Fuel Injectors are only a nozzle and a valve that is controlled electrically. The power to inject the fuel comes from the electric fuel pump that is located in the fuel tank in cars from the late 1980's. An Injector capable of opening and closing many times per second.

When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel -- to make as fine a mist as possible so that it can burn easily.

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.

The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.

Do you need to add fuel cleaner additives to your fuel tank, NO!! Do the fuel injector cleaners work that are added to the fuel tank, NO!! Do not waist your money an these products. Gasoline that you buy at the pump already has these detergents added to the fuel to begin with. If you suspect your injectors are slightly clogged, they can be clean, but only with a stand alone fuel injector cleaning tool. Read expensive ( around $500.00 ) or around $69.95 if you take it and have it done at a local shop that has the equipment.


All engines used in this section have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions. The Powertrain Control Module (PCM) operates the fuel injection system.

The PCM regulates:

Various sensors provide the inputs necessary for the PCM to correctly operate these systems. In addition to the sensors, various switches also provide inputs to the PCM.

The PCM can adapt its programming to meet changing operating conditions.

Fuel is injected into the intake port above the intake valve in precise metered amounts through electrically operated injectors. The PCM fires the injectors in a specific sequence. Under most operating conditions, the PCM maintains an air fuel ratio of 14.7 parts air to 1 part fuel by constantly adjusting injector pulse width. Injector pulse width is the length of time the injector is open.

The PCM adjusts injector pulse width by opening and closing the ground path to the injector. Engine RPM (speed) and manifold absolute pressure (air density) are the primary inputs that determine injector pulse width.


Proper Octane - The octane rating of a spark ignition engine fuel is the knock resistance (anti-knock rating) compared to a mixture of iso-octane. By definition, isooctane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same autoignition resistance as the described mixture.

Is Higher Octane Better?