98 F-150 Hard Idleing When Cold

Have A 98 F-150 4.6l.i Live In Wisconsin And When Its Cold
Outside Truck Has A Hard Time Idleing I Have Have My Foot
On The Accleerator And Feather The Pedal To Keep Running
After About 15 Sec Of This It Will Idle Alright By Itself.

Thanks For Your Input