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The Tweecer logs these as 3.2v & 4.9v values. Here is a graph of the two output levels that signify out-of-tolerance values that cause correction factors to be calculated by the EEC and applied to the injector pulse width as well as being written to correction tables in KAM, which is called Adaptive Control. 8 volts, then the engine is running too lean or too rich. If the output of the O2 (HEGO) sensors stay either below. Closed Loop operation consists of an EEC controller that uses a target air/fuel ration contained in lookup tables (based on a Ford test engine) that uses the O2 sensors as feedback for making adjustments. During Open loop operation, the O2 sensors are not used to trim air/fuel mixture and hence the name "open" loop. The EEC starts in Open Loop and based upon time and engine parameters such as engine temperature, changes to Closed Loop. There are two methods of EEC fuel control, Open Loop and Closed Loop. The EEC calculates this time by monitoring sensors, and calculating "on" time based upon fuel flow for a 19lb fuel injector at 39 psi for a targeted air/fuel ratio that is stored in a multi-dimensional table for engine conditions as monitored from the engine sensors. The EEC does not control injector "on" time from just a *single table *. In the MAF cars, the Barometric Absolute Pressure sensor measures barometric pressure directly and continuously. When the ignition is first turned on, the EEC takes a quick reading of the MAP and stores that value as atmospheric barometric pressure for calculations during running. The SD system uses a Manifold Absolute Pressure sensor (MAP), which measures the absolute pressure (vacuum) in the intake manifold. Both the MAF and SD systems use barometric compensation with the exception of the ‘94-’95 Mustangs which incorporate that function into the MAF.
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The air temperature sensor, the engine temperature sensor, and the Oxygen Sensors (O2 or HEGO) are also used to help determine fuel and timing requirements. By measuring the *MASS* of the air, this helps to compensates for air density changes that occur with altitude and weather changes. The mass airflow sensor measures the *MASS* of the air going into the engine. They are widely published on many web sites and so, will not be listed here.ĭetermining how much fuel to deliver is accomplished in two ways, Speed Density (SD) control or Mass Air Flow (MAF) control. Stored codes are very useful in determining potential trouble. If the car battery is disconnected, or if the battery voltage falls too low, the KAM is preserved capacitors internal to the EEC. KAM receives its power directly from the battery. Conditions found during Continuous operation are stored in special memory called "Keep Alive Memory" (KAM), which is 128kb of read/write memory. Continuous is on anytime the EEC is in operation. On-Demand is conducted during key-on/engine-off and during engine running modes to allow the EEC to test itself. Two types of diagnostics are present in the EEC, On-Demand and Continuous. The EEC objectives include calculating required command values and outputting the required voltages to command, in real time, the spark timing, the EGR valve position, and for controlling the on/off duty cycle of the fuel injectors. Many thanks to Authors such as Tom Cloud, Mike Wesley who have technical articles on the net, Charles Probst, who authored the "Official Ford Mustang 5.0 Technical Reference & Performance Handbook from which information was derived, and Mustang Forum members such as Rick Wagner, who used a EEC-Tuner âĪnd TransmarrowBird Eater (Dave) for sending me his TwEECer â I don’t know that I can improve on the explanation of this information by pulling it into one document, but I am willing to try for the benefit of fellow Stangers. I have spent significant amount of time searching for information regarding the EEC and I have come across readily available reliable sources of information. There are a lot of questions regarding the way the Mustang EEC IV works.