2000 durango hard start

We have a 2000 durango with the 5.9 and on cooler mornings, it will not stay running. It will start and die instantly. It will only stay running if foot stays on gas a bit. Warm weather is fine. The plugs, cap, rotor, wires, and air filter were replaced. It is not throwing any codes at all. 2 mechanics looked at it and gave up. Does anyone have any idea's before I have to take to the dealer???
Thank you in advance, Dennis

I would replace the iac and clean the throttle body you may also have yo reset the iac counts or drive it a while until the pcm relearns the adaptives