1983 Ford C-8000 : CAT 3208 Rough Idle
 

Started having an issue with my truck about a week ago. When I am stopped and in drive my RPMs will drop and then the engine will begin to surge. This does not happen if I put the truck in neutral at a stop. The truck has not died on me yet, however, everytime it begins to surge I feel like it's about to quit. Besides this issue it is running fantastic. I put new fuel filters on a couple of months ago and did not change anything with the truck prior to this problem occuring.

Any help with the problem would be greatly appreciated!

First thing that comes to mind is the actual idle speed. Then, possible fuel line leaking, or I should say sucking in air. Third, possibly fuel pressure, but not likely the issue.