My 1993 eclipse has a new recondition head. The engine runs great but now has a surging idle. I had it put on computer at a Firestone and at my local Mitsubishi dealer. The first test the engine would not respond to any adjustments. The second test,read problem with temt sensor and isc switch. I had both parts from previous engine that ran fine before this problem occured. Can you help?

Phillip,
It's not uncommon for an ISC motor to go bad. Many times, when something is done to an engine such as replacing timing belts, modifying intake, or even a head rebuild can throw off the idle setting. Your ISC motor can pretty easily be tested. A Haynes or Chiltons repair manual will be able to give you the procedure to test it yourself. I'm not sure why your temperature sensor would through an error, but I don't think that has anything to do with your idle surging.

Idle surge is a common problem, and ISC motor do go bad over time. They give little to no warning when they go bad. But an idle surge is the common symptom. Another thing you can check is your car's computer itself. Read this article for further information:
http://90gsx.com/eclipse/cap/caps.htm

If your ECU is malfuncitoning, that can also lead to your engine acting abnormal and falses errors being sent. Pull it out and have it checked.
Good luck!