Rochester Quadrajet issue

[83c10_Owner]

I have a Rochester Quadrajet carb 17083224 on a 83 c10 Silverado with a 305 engine. Also everything is stock. My question is, trying to adjust the carbs fast idle and it effects the curb idle. Well I try to fix the curb idle and the fast idle is affected also the next morning. I’m still learning on the carb so is it a vacuum issue or something else. It acts that way during cold or cooler weather not in warmer weather.

 

[fast 99]

When choke is completely warmed fast idle on right side shouldn't change idle speed. Either choke isn't warmed enough [no preheat], bad choke thermostat [check for open circuit ohm it] linkage is stuck and/or not adjusted correctly. Try pushing down on the fast idle cam with a finger. Needs 12v power on electrical lead at choke thermostat. There are several other adjustments that will effect cold operation but this is where you should start.