intermittent check engine light

I finish my conversion within the last month an ej22 out of 94 legacy  into a 85 westy. Now I’m getting around to testing it on the freeway.  I’ve been getting an intermittent check engine light. Sometimes it will come on for five or ten minutes and then shut off. Other times it will come on and stay on, but when I shut the engine down and preceded to plug in the green connectors it won’t throw any codes. However, when I plug the black connectors it throws out code 24 Iac  valve +32 02 sensor. I also, started driving around with the green connectors just to see what would happen and it has thrown-out the code 32 but I haven’t seen code 24 yet. The 02 sensor is brand new , and I cleaned out the IAC before I began the conversion.  As of right now, the engine idles and accelerates with no problem. I checked all the hoses and 02 sensor connection and everything seem to be ok. Not sure what to make of the problem; and I wanted to get some ideas on how to go about diagnosing the problem. Thank you

Edited February 6, 201511 yr by JC20