Stumble/Chug driving off after cold start

2007 6 cyl Accord EX-L sedan, 56,000 properly maintained miles. No check engine light, no obvious loose/damaged wires or hoses.
On morning cold start in Park-- catches immediately with RPM about
1100-1200. Idle is a bit rough-- though accelerates smoothly up to 3000-4000 in Park. After a few minutes, RPM drops to around 800 or so, idle still a bit rough.
The problem though is driving off at any point in these first few minutes, car chugs/stumbles right before up-shift point. The colder the outside temperature, the worse it is. After driving for several more minutes though, car then operates normally until restating the next morning.
Also, after a cold start, if I let it idle until the thermostat opens and the fan cycles on, it drives off normally.
Any idea what the problem is?
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On 4/23/2015 2:01 PM, H.L. Hunley wrote:

Air in the cooling system.
Bleed it.
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On 4/23/15 2:07 PM, News wrote:

Well, did that. There wasn't really any air in there. Still doing it :-(
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