My fox does the same exact thing. If you find out what it is lemme know.
When its warm how does your car idle?
Since the morning temps are now getting below 50, when I cold start my Fox (88' cis basic) the motor shoots up to 2000 rpm right away, then settles down to 1500. As it warms up, it gradually drops down to 900 rpm, just where it should be.
I suspect that having the timing set to 14 might has something to do with it, but what exactly on the cis basic system controls cold start flare up? I'd love to dial it down a bit......
The auxiliary air regulator is what controls the "cold idle." It's located at the end/under the intake manifold by the throttle body. A heating element causes a bimetallic strip inside the regulator to bend and reduce extra metered air as the car warms up. They aren't supposed to require adjustments, but it may be possible.
2k ain't bad for a cold start rpm, although I'd be expecting that from below-freezing temperatures, not 50*F...
If you want to play with it, you'll have to remove the AAR probably. There's a nut on it that adjusts the pretension I'm imagining. Mark it beforehand so you know where you started from if you need to go back.
I really suck at smog.
So this morning, I popped the hood, traced the aux air valve, felt around the air hose to make sure it wasn't split or otherwise compromised, it seemed totally fine. Got in, started and perfect start this time!
Revved itself to 1500 rpm, then settled to a reasonable 1200 rpm cold idle.
Time will tell, but maybe the aux air valve was just out of practice from never being called into action all summer/
That's the hope anyways