my 93 2600 with 240000Km has been working fine however for the past several weeks it has started to idle extremely high on start up when cold. This usually happens when I first start it in the morning and will last for approx 3 to 5 min and then go back to normal idle and its usually ok for the rest of the day.
Any suggestions??

my b2200 does it too. try using a thinner oil. i think it's just the way the truck is.. i live in canada... usually idles around 2000+ rpm's in the winter. -10c or less

Dude, my B2200 does it, since they have carbs on them, it is the elecrtic Choke on it and it goes off after 5- 10 mintues when its really cold out correct? do you usally pump the gas and it goes off its the choke. its suppost to do it.( after its warmed up enough)