I have a 2004 frontier quad cab since new. Lately I've had a sticking throttle. When warm (bout an hour of driving) from a standstill, my gas pedal won't move. The issue is not with the cable or pedal but at the throttle itself. It doesn't budge until u break it free by jamming on the gas pedal. it usually does this for about 15-20 minutes and then stops and acts normally. Any ideas what the problem could be?