1960s 1966 Eldorado carb question

[Julien Abrahams]

So the '66 Eldorado that had been in storage for 30 years is now running and driving. One thing I noticed is that on startup, the idle is about 200 rpms faster for the first couple of seconds after firing. Then it settles down to either high idle when cold or bade idle when warm. . I am just wondering if this is normal because my '67 does not do this.
Differences between the two cars: the Eldorado is a California car so it has the A.I.R.system. it also has a Carter AFB (whereas my '67 is a non California car with a Rochester Quadrajet).
The Eldorado runs fine but I was wondering if perhaps the faster idle for a couple of seconds is something to be concerned about. I believe it might have something to do with the A.I.R. system?
Thank you in advance.

[TJ Hopland]

I work on more QJ's than AFBs but I seem to recall their choke and fast idle mechanisms are similar and depend on fairly crude components and pivots and gravity to work properly.  And again from fuzzy memory I don't recall the AFB having any vac canisters on it?  QJ's often did and depending on how many if they had anything to do with the choke and warm up stuff.  It could be that they are just different but it could be that something is worn or sticking in the AFB. 

Things like a little wear in the throttle shafts change the angles where the interaction is with the cams that are attached to the choke.  I don't know how bad the AFBs wear but the Q jets are kinda known for worn throttle shaft bores.  If you had a QJ on a manual trans those bores could be pretty much gone at 50k miles. 

[69Deville]

My 1966 Series 60 (Carter and AIR) does the exact same thing. I have always wondered if this is normal as I rebuilt the carb to using the service manual and it made no difference.

Curious if this is normal as well.