![]() ![]() Most auto repairs shops charge between 75 and 150 per hour. Some V6 Mazda vehicles (Tribute, MPV) also have this issue where the rubber elbow at the back of the intake manifold rips through, causing a vacuum leak and the code P0171. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder. Mass airflow sensors (MAF), which are used on a variety of multiport fuel injection systems, come in two basic varieties: hot wire and hot film.A cracked or ripped intake boot is a common reason for the code P0171 in many BMW vehicles. Though slightly different in design, both types of sensors measure the volume and density of the air entering the engine so the computer can calculate how much fuel is needed to maintain the correct fuel mixture. Mass airflow sensors have no moving parts. Unlike a vane airflow meter that uses a spring-loaded flap, mass airflow sensors use electrical current to measure airflow. ![]() ![]() The sensing element, which is either a platinum wire (hot wire) or nickel foil grid (hot film), is heated electrically to keep it a certain number of degrees hotter than the incoming air. In the case of hot film MAFs, the grid is heated to 75 degrees C. With the hot wire sensors, the wire is heated to 100 degrees C. As air flows past the sensing element, it cools the element and increases the current needed to keep the element hot. Because the cooling effect varies directly with the temperature, density and humidity of the incoming air, the amount of current needed to keep the element hot is directly proportional to the air "mass" entering the engine. MAF sensor output to the computer depends on the type of sensor used. ![]() The hot wire version, which Bosch introduced back in '79 on its LH-Jetronic fuel injection systems and is used on a number of multiport systems including GM's 5.0L and 5.7L Tuned Port Injection (TPI) engines, generates an analog voltage signal that varies from 0 to 5 volts. Output at idle is usually 0.4 to 0.8 volts increasing up to 4.5 to 5.0 volts at wide open throttle.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |