I have read all the post on this subject and as usual several key elements are left out that can attribute to poor driveability and performance. The EEC4 has a vast amount of capability to adjust to most minor modifications without requiring a performance chip. Unfortunately those who buy a performance chip are unaware of the limitations imposed by law and the manufacturer, that limit fuel trim and ignition strategy alteration.
As a Master Journeyman Tech with over 32 yrs specialization on Ford Performance vehicles plus training with Ford and Intel on their computers I have witnessed too much disinformation on the electronic engine management systems. Scott Halliday and his dedicated moderators have provided Mustang Enthusiasts an excellent site with the best possible tech source available for both the hobbyist and proffessional Mustang Owners. In support of their committment the following information is provided on reprogramming an EEC4 after repairs or minor mods to the engine and it's electronic engine management system components.
First relates to maintenance/repair of engine or replacement of EEC Sensors or Fuel Injection Service. The vehicle negative terminal must be disconnected for 30 minutes. This allows the EEC to unload its Random Access Memory Chip of its last calibration based on the engine mechanical condition and sensor data. Reconnect the battery and restart the engine. Turn on all high load electrical components (A/C, High Fan, HiBeam Headlights) then turn the steering wheel full left and full right. This signals the EEC to start relearn. Then take thge vehicle on a operational run as follows.
1. 1 mile of city driving in normal strop and go traffic.
2. Enter a highway that will allow you to come to a full stop for 1minnute
on the side of the road. Then accelerate at wide open throttle to
highway posted speed.
3. Then maintain a cruise speed for 5 miles.
4. Re-enter into the city and drive at normal traffic speed for 1 mile
before returning home and shutting the engine off.
It will probaly take about 300 re-starts during daily driving before the EEC is finally reset to all engine temps and driving habits of the driver. Remember the EEC enter false close loop at 165-180F and true closed loop at 195F.
Second procedure is only done when the engine has had major repairs or replacement, which requires the battery to be disconnected for a period of 24 hrs. This is normally already been done as the engine is being repaired since the battery is already disconnected. Then after the repairs or mods follow the previous steps in the first re-learn directions.
Remember that the EEC4 is far more advanced than the other manufacturers EECs because it is the only true dedicated automotive EEC that processes 2 million bits of info per second.
Mike Geddry Sr
Regional Director
Mustang SVO Owners Association
Pacific Southwestern Region
Owner/Master Tech
Dr. Mustang
Resetting EEC4 PCM 
