stalling after start on cold mornings

I recently changed my timing belt and serviced the transmission (so I was told by the mechanic). Now in the colder weather, my 2004 Odyssey starts in the morning but stalls as soon as I shift to the drive or tap the gas pedal. Thereafter, the engine would not start until I crank it several times over a long time (5 to 10 minutes) and floor the gas pedal. Then, the engine would shake and backfire and only would run if I keep it on a high RPM. By the way, this Odyssey passed the California smog check last week with flying colors and has no loss of power or bad running with the engine is not cold. Does anyone know where the problem is?
Thanks,