Started screwin the screw in ad checking for run away, got it till it won't go farther in and truck went from 900rpms to 1100 at idle, then if it tap the throttle it would jump to 1900 then go all the way to 400 almost die then fire up to 1100. So I stood on it till 3000 then let off and the truck just shut off. I put the idle screw all the way in from front to firewall and didn't make a difference. Any time I move the FP screw in it does this. Any ideas?