I was changing my valve cover gasket this evening and when I got all finished up I started my truck and without touching the gas it was running idle wide open. Checked the throttle cable it was fine. Tell me what you guys think

 

It would be nice if we knew the year , engine,and model truck you have ! Since you mentioned a throttle cable at least we might be safe thinking it did not have an electronic throttle control. Can you help us out there?