This is such a vague question with very little info to go on. So many possible causes. Do the easy free checks first... First thing, pull the codes. Code 12 is normal, Let us know what you find. Next, check for vacuum leaks at all the lines and the base gasket of the throttle body. Check all your plug wires for any burns or cracking. When was the last time this thing had a tune up and the air and fuel filters changed?
Next write up a detailed description of what the truck is actually doing, so guys don't just throw out random guesses that will end up causing you to waste money throwing parts at a problem... Not trying to be a jerk, just trying to help!!!
