I am assuming it's an automatic. Are you saying it idles high, causing the vehicle to move without pressing the accelerator? If it idles high, checkout the surging idle checklist (sticky) in the 5.0 forum, theres a wealth of info on what to do to solve it. Most of the engine controls preform the same function on the 5.0 as on the 2.3, so most of the info in there should apply to your 2.3.