So guys, I've got my dad's 1989 F-150 302 w/4 spd manual....When it gets started after it sits for a while....it will shudder and start to stall, if you give it some pedal it revs up and acts fine, if you let off it starts shuddering and you can watch the RPM's go from bout 750~800 down to 500 and below....then it will stall and die....any ideas whats causing this?

 

Ford Fuel Injection » Idle Air Bypass (IAB) Here is what I would look at first. You can clean it with carb cleaner but don`t get any cleaner in the electrical parts.
Also, from the list on the right of that page, click on Self Test and check for any trouble codes.

 

Wow lol, i bet that is the problem too, cause after you run it consistently for a few days, it wont do it anymore cause your moving that damn spring. thanks Lazy K