I just got an 83 z28 5.0 ho. When cold start it idles around 2200. it idles around 1400 when warm. If I shut it off start it without touching the throttle it idles nice and low around 750 but as soon as I touch the throttle it jumps back up and stays there. Any suggestions?

 

High idle cam. That green weight/lever on the passenger side of the carb. The weight end is supposed to drop down when the choke is fully warmed and open, which disengages the high idle cam on the other end. Either your choke thermostat isn't opening up the choke fully, or the mechanism is not free to move like it needs to.

By any chance is your "choke" light staying on?

 

No and it runs strong just idles high

 

Check your spring that pulls the throttle closed whenever you let off the gas.


Mine was worn out, put a new one on, fixed it.