STILL lean and rich? more thoughts?

I don't understand how your computer can be too old to get the codes. I use an 89 eec in my car and I'm able to pull the codes w/ a testlight and a jumper wire. I don't understand how your car can be running both rich and lean at the same time either?

I posted the answer to your question in one of your previous posts. The check engine light DOES NOT HAVE TO BE ON to dump the codes.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

If your mechanic is so uneducated that he can't dump the codes, I recommend that you take the car to the Ford dealership. They will charge you an outrageous price, but will have some idea of what they are doing.

Buy a shop manual and qiut wasting your money on a mechanic that needs some remedial training. Frankly I wouldn't trust him anyway. A Chilton's manual for your Mustang is less than $25.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $20 from Borders.com see http://www.amazon.com/ . Select boo...very good, and I found it to be very helpful.