hey guys i have an 03 ram 1500 with a 4.7. last night on my way to work i was sitting at a traffic light and the truck died. i started it back up and it was idling really low, so i reved it up to agout 2000 rpm and knotided that it wouldnt stay at 2000 rpm. it would drop and then go back up and then drop and go back up. but as soon as i started moving and shifting through to gears it was fine. it acts like its not getting enough gas .anyone have any ideas as to what is causing this????