The ECU, or engine control unit, is the computer that runs the engine in a Ford car or truck. By modifying the software that runs on the ECU you can increase the power and torque figures of your Ford. Modifying the ECU is called flashing and can be done through a number of methods, from simply plugging in a software module to the diagnostic port all the way to physically soldering a chip onto the motherboard of the ECU itself.
Determine the year, model and power train in your Ford as well as any other modifications previously made to your car or truck. This is important because not all engines can be flashed, generally it becomes prohibitively difficult for pre 1990 Fords. Generally flash software will only work within a specific family of engines so you need to buy the right brand and model of flasher. Car modifications may necessitate a trip to a dynometer to properly calibrate the flashing software. Dynometers measure the power output of a car and require the assistance of an expert to use this data with a ECU flasher.
Determine which flasher system you need for your Ford. There are three kinds of ECU flashers: the software flash, the plug-in/soldered chip and the inline flasher. Each has its advantages and drawback, though not all options are available for all engines and you will need to research your specific power train. The software flash is the easiest to install, in most cases, with the software loaded onto the pre-existing electronics. The plug-in/soldered option is the hardest because you must plug another chip into the circuit board or even solder it on, which carries the greatest risk of damage. A newer option of a plug-in flasher is available, whereby the flashed chip is plugged in between the wires going from the ECU to the engine. This is the easiest to install, though not many cars are currently supported.
Install the software flasher by plugging in the flasher module to the diagnostic port on your Ford. On most Fords the port will be located under the driver side dash. Some require the car to be off, some require it to be on. Once it is plugged in, follow the instructions included in the kit. These usually require entering codes for your chosen level of performance because the flasher is capable of variable levels of horsepower and torque boosting. This method is reversible, in most circumstances, though some flashes can only be reset by special machines at dealerships.
Install the plug-in chip by opening the ECU box after turning off your Ford. The kit will tell you where to plug in the chip --- usually the diagnostic port. To install the solder chip, you typically must remove another chip or attach the chip at a junction. Exercise caution and, if you have any doubts, seek expert assistance. You can damage your Ford if you connect the wrong wires with solder. This method is irreversible.
Install the plug-in inline flasher --- which resides on a chip in a special wire. Locate the control wire from the ECU to the engine. The car needs to be off when you plug the wire in. Turn on the car and you should have an instant power gain. If you want to return to stock performance, turn off the car, unplug the wire and reconnect the old wire.
If you have any doubts about doing this yourself, don't do the installation. Go to a professional auto shop that specialises in ECU flashing or aftermarket modifications. Shop personnel have years of experience with flashing and may even offer a warranty on the work.