1998 Acura CL IDLE PROBLEM

MY VEHICLE RUNS GREAT AND HAS PLENTY OF ACCELERATION. My problem is that the vehicle will not hold idle after being driven for as little as 20 minutes at normal operating temp. When vehicle sits for at least 25-45 minutes and will try to start but will not set up and idle it stalls. I must hold the gas pedal down slightly to hold the idle for a minute to clear the engine then the engine runs smooth again and no problem driving away. there is heat problem or something like it as it does the same thing day after day

I have replace the IAC a week ago and not change in symptoms Is it fuel related such as a vapor lock problem??

please advise

thanks

rp