If the engine is running rich less oxygen in the exhaust , the computer shortens the pulse width of the injectors to lean the fuel mixture.
It is located on the side of the throttle body and uses a variable resistor that changes resistance as the throttle opens and closes. It may be mounted on the intake manifold or attached to the intake manifold with a vacuum hose.
The temperature of the air entering the engine must also be monitored to compensate for changes in air density that occur colder air is denser than hot air. This tells the computer when the engine is cold and when it is at normal operating temperature.
The computer needs to know the temperature because a cold engine requires a richer fuel mixture when it is first started. When the coolant reaches a certain temperature, the engine goes into Closed Loop operation, which means it starts using inputs from the oxygen sensors to fine tune the fuel mixture. When it is operating in Open Loop when cold or when there is no signal from the coolant sensor , the fuel mixture is fixed and does not change. Faulty inputs from any of the engine's sensors may cause drivability, emissions or performance problems.
Reading the code s with a scan tool will help you diagnose the problem. Idle speed on fuel injected engines is computer controlled via an idle air bypass circuit on the throttle body. A small electric motor or solenoid is used to open and close the bypass orifice.
The larger the opening, the greater the volume of air that can bypass the throttle plates and the faster the idle speed. On newer vehicles with electronic throttle control, the computer also controls the opening of the throttle plate when the driver pushes down on the gas pedal. Position sensors in the gas pedal signal the computer how far to open the throttle plate. Idle problems on EFI systems can be caused by varnish and dirt deposits in the throttle body idle control circuit.
Cleaning the throttle body with throttle body cleaner can often solve idle problems follow the directions on the product. Idle problems can also be caused by air leaks between the airflow sensor and throttle, the throttle body and intake manifold, and the intake manifold and cylinder head s , or in the PCV or EGR systems, or vacuum hoses.
A fuel injector is nothing more than a spring-loaded solenoid pintle valve. When energized by the computer, the solenoid pulls the valve open. This allows fuel to spray out of the nozzle and into the engine.
When the computer cuts the circuit that powers the injector, the valve inside the injector snaps shut and fuel delivery stops. The total amount of fuel delivered is controlled by cycling the injector voltage on and off very rapidly.
The longer the pulse width, the greater the volume of fuel delivered and the richer the fuel mixture. Decreasing the duration of the injector signal pulse reduces the volume of fuel delivered and leans out the mixture. Dirty fuel injectors are a common problem.
A buildup of fuel varnish deposits inside the tip of the injector spray nozzle can restrict fuel delivery and interfere with the creation of a good spray pattern. This can cause a lean fuel condition and misfiring. Cleaning the injectors with fuel injection cleaner, or removing the injectors and having them cleaned on a fuel injector cleaning machine can usually restore normal operation. Using a Top Tier gasoline that contains adequate levels of injector cleaner can also prevent varnish deposits from forming.
Another important factor that helps determine how much fuel is delivered through an injector when it is pulsed, and that is the fuel pressure behind it. The higher the pressure behind the injector, the greater the volume of fuel that will spray out of the injector when it is opened. Fuel pressure is generated by a high pressure electric fuel pump usually mounted inside or near the fuel tank.
Pump output pressure may range anywhere from 8 to 80 lbs. The pump usually has an pressure valve to vent excess pressure and a check valve to maintain system pressure when the ignition is off. In a multiport EFI system, the pressure differential between the fuel behind the injectors and the vacuum or pressure in the intake manifold is a constantly changing variable.
Under light load or at idle, a relatively high vacuum exists in the intake manifold. Once the engine starts and the manifold vacuum is available, the diaphragm opens a valve and allows unused fuel to return to the tank. Air is delivered to the engine through the throttle valve. This throttle valve operates like the throttle valve on a carburetor--as the throttle is opened, more air is allowed to enter the engine.
Where the throttle body injector differs from the carburetor is in the area of idle control. This valve is in effect a computer-controlled vacuum leak. To increase idle speed, the valve opens to allow more air in. To lower idle speed, the valve closes to allow less air in to the engine. I tagged each injector and shipped them to ProFlow. When Greg tested the injectors before cleaning, the flow patterns were all over the map, and the flow rates wildly different.
He took extra effort to ultrasonically clean the ones that were especially badly clogged until he got the flow rates close to each other. They were mailed back within a week, with before and after flow rates and resistance levels checked, and every injector inscribed with the tagged number.
They kept me informed at all points along the way about their progress. These are ultra rare injectors as Honda does not make spares for this bike. I would trust ProFlow again with these. Good job, guys! The bike went to the dyno before the work and make with an unsteady fuel flow. After the motor refresh rings, degree cams, etc. Thanks again, this service is def worth the money! I just wanted to say thanks to Greg for a very quick turn around on my injectors for our Sea Doo.
He was honest and knowledgable about his craft. I have since given his name to a couple of my friends, one of whom owns a cycle repair shop and another who owns watercraft repair store. It runs great!! Thanks Michael W. OK, one week exactly and they are back and ready to install. They left last Tuesday and they are here today. Very nice. They do all the injector service on all my bikes. Very happy with the service they provide. Your cleaning job fixed all the problems my Viper was experiencing.
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