low idle

Ok here is my problem I just got a 2000 siverado 4x4 and in the morning when it is cool out the truck dosen't have a high idle. when I start it it will go to 800 rpm for 5 seconds then back down to 500 rpm. if I let it warm up by giving it a little gas 1100-1200 rmp for 45 seconds it runs fine if not it sounds like it might stall. Ok history 4.8 new gm platinum plugs cleaned Tbody and replaced air idle control valve. On real cold mornings I have a idle of 1100 for a min. then slowly goes down great but if it is not to cold no high idle. Could it be a coolent sensor or air sensor. Other than that the truck runs great any help would be great Thanks.

Did you ever find out anything on this? I am having the same problem with mine.

Yes I changed the air idle control valve $115.00 and cleaned the T.body with a good T. body cleaner not carb cleaner now first thing in the am start up 1200 -1400 for a minute or to then slowly drops down to 750 then once it is warmed up 500. Oh yea also run high test gas every other fill. :iceslolan

Thanks. I will give that a try.

It ended up being a vacuum leak on the intake manifold.
Thanks for yuor help.