Mitsubishi Repair: 90 eclipse 1.8 idle problem, mass air sensor, coolant temp

Question
90 eclipse 1.8 auto I rebuilt the engine it was running great then it started this idle problem it would go from 1500 to 3000 when it started doing this it would not start when it was hot. I reset all of the idle to 750 and timing  and I got 2 codes coolant temp sensor and o2 sensor and changed them. If I unplug the the idle speed control it stays at a smoth idle. the idle speed motor move up and down fine and the idle position switch checks out fine my next step was to check the motor position sensor but the book does not say where it is located. What else should I check this thing is driving me crazy Can You Please Help?
Thank You
Jeff

Answer
Jeff,
It's a good idea to check your car's computer.  Read this article for further information:
http://www.90gsx.com/eclipse/cap/caps.htm

If your ECU is faulty, it'll cause all sorts of problems.  Unplugging the ISC prevents the ECU from trying to adjust the idle. And if your problem is the ECU, it makes sense your idle returns to normal when you unplug the ECU.  But I would also recommend you check your EGR valve and your Mass Air Sensor as well.  
Good luck!