99 Accord V6 J30 engine 159,000, having idle.

99 Accord V6 J30 engine 159,000, having idle problems when hot. When cold, everything is normal. It only occurs when after the engine has reached normal operating temperatures. For example, I stop for more than 15 min. I start the car and it doesn't want to idle. Doesn't do it every time, but it has become more frequent lately. When this condition happpens I have to nurse the throttle to bring it back to normal idle for about a minute, otherwise engine stalls. If I' am sucsessful to nurse it back, after some engine missing and rough running, then it idles fine. If I stop shortly, like to get gas or quick stop, less than 10 min its ok, idles good. I have already replaced the IAC (Idle Control Valve) at 140,000 miles ago and cleaned out the throttle body. I have no Check eng. Light indication. This problem started around 150,000 miles ago. Where should I start looking? Thanks for any advice!