Loping Idle on Cold AMs Until in Gear

[The Speaker Guy]

Hi All - My 1994 B3k idles weird on colder mornings (i.e. 60F and below in California). When it is started, it fires right up to about 1.2kRPM, then starts dropping down to about 400. The voltmeter plummets to 8V or so. After a second or two, it revs to 1.2k or so again. As soon as I put the car in gear, it corrects to an appropriate idle in a second or two, and the problem is gone until the next morning.

IAC?

MAF?

Thanks