Toyota Repair: 2001 Sienna Idle Problem, siennas, inclement weather

Question
This has happened a couple of times now. 2001 Sienna LE after starting dies immediately as if there is no idle. I say no idle because it can be kept running with a foot on the accelerator. The last time after several attempts I noticed a small backfire then it worked and has done so since.

Factors that may or may not be related. Both times this happened was after it sat awhile (3 days) during periods of inclement weather (rain, cold - 30-40 deg). Also, I've noticed what seems to be a delay in shifting when starting out in cold (30-40 deg) conditions......Thanks...

Answer
This is nopt uncommon on Siennas and also Camrys, the problem is the idle speed control valve, it's located on the throttle body and can only be removed by removing the throttle body, it can then be cleaned and the carbon that has built up in the valve is removed, the idle should return to normal after doing this.