Hello. Can you help me. I hope you can. I have honda civic coupe 98 non vtec. When engine runnig cold is OK, but when engine getting normal temperature the idles erratically. It is between 1000 and 2000.I checked idle air control valve, throttle position sensor, oxsigen sensor and many more. They look OK. Malfunction lamp is off. What is the problem then?
Thanks for answers.

Check Fast Idle Thermo Valve, in the throttle body, and igniter. Make sure all vacuum hoses and connections are good.

Thanks for answer. You was first.