idle surging

[dirttrackin68]

2002 7.3 PSD Completely Stock. I recently bought this truck. It starts great, runs good..

When @ idle (when cold) the engine surges. I can hear it through the exhaust. Loud "WOOSH". It seems to go into cycles of 20 second intervals. From the "WOOSHING" to normal idle, then to the "WOOSH"..normal..

any suggestions??

thanks much

[daboostcreep]

exhaust bypass valve

[dirttrackin68]

is that valve something that must be replaced? or would unplugging it hurt?

Thanks