How many miles are on the car?
Have you checked for vacuum leaks?
Have you checked for air leaks?
How old is the O2 sensor?
When was the last time you cleaned the MAF sensor?
When was the last time you cleaned the IAC or throttle body?
When was the last time you changed the PCV valve?  Have you checked
it?
When was the last time you changed the spark plgs or plug wires?
When was the last time you changed the air filter, breather element,
or fuel filter?

The check engine light comes on becasue there is something wrong.
Duh.  if it has an EEC-IV computer in it (I suspect that it does) it
is real easy to read the codes.  Do an internet search on it.

I usually use the instructions posted here:
http://www.thorssell.net/hbook/eectest.html

And get a MityVac http://www.mityvac.com

I am inclined to believe that you are not maintaining the car.  I
drive a 1995 Escort that has about 150,000 miles on it and it idles
perfectly.