Idle Issue.. Please Help!

[808countryside]

I have a 1985 Nissan 720 king cab pick-up.

Problem: When I start the truck in the morning (cold start) and let the truck warm up for about 5 mins. ( i live in oahu, hawaii so it doesn't get that cold). my idle is fairly low, but as im driving to work about 30 miles into getting to work. the trucks Idle seems the be alot higher. so, i adjusted the idle by the carb (idle screw), which the idle does go lower, but the problems still seems the happen. the truck still has an High Idle once i start driving again?? What could it be??

[PEZi]

sounds to me like a vacuum issue to me... i had the exact same problem a long time ago, replaced the lines and it was good to go.

start there