hey i got a 89 f150 MT 5 speed and the truck high idles around 100-1100 sometimes but the other times it will idle around 750 witch is perfect. i noticed something funny yesterday while i was driving in 4th gear i let off the gas and the truck drove itself it felt like letting off the brake in a automatic car and it just kept going. i also felt inbetween shifts its better if i let off the gas for a couple seconds then push in the clutch. if i do it normally the rpms will shoot up. it feels like the tps sensor is lagging to a closed throttle. anyone else?

 

Clean the IAC valve and check the throttle cable for tight spots. More than likely the IAC needs cleaned.