Surges at idle

[femurphy77]

Yes I did a search and no this one isn't like any of the other idle issues I saw. If I let my '00 eddie bauer 5.0 awd sit and idle long enough the idle will start surging up and then dropping below normal idle speed. If you let it go long enough the surge rpm creeps higher and higher and the drop goes lower and lower until it dies. If I try pushing on the gas pedal to artificially raise the idle to say 2000 rpm the surging and dropping still continue until it dies. No codes, no apparent vacuum leaks and no other symptoms, i.e. mpg changes, overheating etc. Any ideas?

Thanks!