interminent check engine light


I'm getting and occasional check engine light coming on at idle. When I drive away say 200' feet it goes off. Seems to idle a little high also. I have checked the TPS and seems fine .410 at idle. I suspect the IAC but it is relatively new and seems OK. Can't find any vacuum leaks. Any ideas????
I have '87's, so if it applies to ' need to find the stored code. If you don't have a scantool, ground the upper two right ADL connectors and watch the SES light. It will flash once, then twice, for a total of three times to say code 12, ecm is good. Then it will flash any codes stored three times. There is good info on this on

Usually my intermittent codes are bad O2 sensors, the ecm will put up the code if the sensor is out of range of its programmed parameters.