Fast Idle Faster!

[DWCaprice2017]

Hi, All!
I have an ‘84 Caprice, 305, with an electronic Quadrajet. Before starting the cold engine, I pump the pedal three times, turn the key, it starts on high idle that’s slightly rough, then after a few minutes on the fast idle, it goes to a slightly faster idle and smooths out!
What the heck is going on?
I have a feeling this problem is why, after tapping the pedal, the slow idle is a bit rough.

 

[69hurstolds]

Vacuum leak? Check vacuum hose connections and hoses for cracks/splits. Tedious process. Also check the carb hold down bolts for tightness. Not uncommon for them to loosen over time. Also, the choke pull off working properly? There's a number of things to check, but long distance checking with one sentence to diagnose over the interwebs is a bit tough.

Has the carb ever been fiddled with? If the adjustments are tweaked, you could have some issues there as well.

 

[jcelk]

after a while when it smooths out thats probably when the computer kicks in and richens it sounds like it;s running lean before the computer kicks as 69hurstolds said check for vacuum leaks make sure all vacuum lines are tight fitting vacuum cheak each line they might look ok but won;t hold vacuum check choke too of course this is just what i would check first . don;t mess with the carb adjustments unless you know what you are doing

 

[79 USA 1]

May be way off base on this but after checking for a vacuum leak as mentioned above check the choke pull off. May be keeping the choke closed causing the rough idle during warm up. As the element warms up the choke is opening allowing the engine to run smoother.