Another Idle Problem Plus Dead Pedal

I am having idle problems when the engine is cold. The idle will drop to 400 rpms for a few seconds then race up to 1100 or more. After a few seconds of high idle it drops to about 800. Then the cycle starts again. This causes the truck to lunge forward and if I don't have my foot firmly on the brake pedal I will hit the car in front of me. Also, while it is doing this I have a dead accelerator pedal. When the light changes to green and I accelerate nothing happens. It takes about 5 seconds or so then the pedal starts working again and I'm on my way. It makes crossing a crowded street in the morning a little risky.
I am going to take it to the dealer but I'd like to know what might be causing the problem before I take it in.

Has anybody had this problem before? Or know what causes it?

Thanks in advance.