Subject: 93 mitsubishi eclipse, 2.0L non trubo gs manual
Question:

When i turn my a/c on the engine idle drops from 800rps to 200rps and contuines to go up and down!And will die after you let off gas!
when you turn the a/c off the engine runs smooth!
I have replaced the (isc motor)twice as directed by auto repair shop,what repair or diagnostic test can i do?
thanks, greg
Answer:

Greg,
Your idle speed may just be set wrong. You can find the procedure to adjust your idle here:
http://www.vfaq.com

You should also have your alternator tested. It may be dying. If you have an AutoZone in your area, they can check your alternator for free.
Good luck!