My truck idles high In park and neutral but seems to run just fine in drive, reverse ect. My idle adjust screw next to the carburetor doesn't seem to have an affect on the problem when adjusted. If any one has any ideas on how to fix this, I would really appreciate the advice. Thanks.

 

I believe the idle speed is adjusted with the dashpot, not the screw. The screw is adjusted to where it almost stalls when the electrical connector on the dashpot is disconnected. You also may have a problem with the choke fast idle linkage/adjustment.