Check Engine Light?
 

Hey guys as of last night my check engine light turns on when i am downshifting. It turns on at about 2500RPM and then goes out when i return to IDLE. If you guys have any ideas let me know. Thanx

------------------
1990 LX 5.0 Moroso Cold air Kit, FRPP 65 mm T-body, Hurst Billet/Plus Shifter, Underdrive pullies,BBK 1 5/8 equal lengths,2 1/2 x-pipe with high flow cats and dynamax mufflers, Kirban Adj Fuel regulator
15.036@92.98mph 5280 feet above sea level, Before T-Body. Wondering what my times would be at sea level. PS 60 ft time was 2.333

Buy yourself a code scanner at your local auto parts. It will give you instructions how to use it and in the long run it will save you time and cash when you do it yourself.
There is another way of checking your codes without a scanner but I can't remember how. Someone else for sure would know aboout that.

------------------
89 Intercepter
BBK Shorty Headers, K@N Cone Filter,H-pipe, Flow Master,Under Drive Pullys,14 degree,Short Belt 14 degree Timming, No Air Silencer, And All Police Package

As far as the other way, use a jumper wire on the Self-Test connecter. Turn your key over to the accessory position and the Check Engine light will give you a series of flashes. These flashes will give you any error code stored in the computer.

A code scanner is as essential for maintaining your Mustang as a set of wrenches and sockets. It will make you much more familiar with your vehicle, allow you to do straightforward diagnostics on your own, and help you with preventative maintainence. It will pay for itself instantly, the very first time you use it. Call around the shops in your area and ask what they charge to diagnose a check engine light condition. After your done, you will see it is $40 bucks well worth spending. I highly recommend the device for every Mustang owner of a 87-93 Fox bodied platform.

Good Luck,
Dan