Blows cold air the faster i go then it starts to blow hot air truck also seems to have small miss and smell of antifreeze under hood this is 4.3 x code please help

Emmit. I assume it blows air, just not hot? If that's the case, the control valve is faulty or probably unhooked. It will be in the heater hoses visable under the hood. Look for an unhooked cable (if its cable type..very visable) or unhooked or damaged vacumn line. Good luck.

check antifreeze levels and look for vacuum leaks under the hood (broken small hoses..etc) there is an emissions sticker under the hood for all the vacuum lines check each one..

if your heater constantly blows cold then there is a problem with water circulation I:e the heater has a small radiator like your engine has a large radiator the small heater radiator is called a matrix instead of just cooling the water passing through it like the radiator for your engine it is designed to give heat via a fan that blows through it so when it fills with hot water from the engine bay the blower fan blows through it thus giving heat inside the car if it is blowing cold then there is no water getting to it or the water is low in engine bay or there is a blockage even possibly a leak or quite simply the switch that controls the flaps to give you hot or cold air is stuck in the cold position with out more info and me asking more questions this is the basic idea of how it works
hope this helps

Is the gauge showing the engine is warming up to normal temp ?
Are the heater hoses getting hot ?
If the heater core is getting hot, it could be a blend door problem. The blend doors direct air thru the heater core and the ac evaporator among other things.

glad you found the problem

You should look under the dash on the passenger side to see if there is any evidence of antifreeze on the bottom of the heater plenium. What usually starts as a small leak in the interior of the plenium will eventually lead to the heater core leaking all over the interior. You are getting steam and the smell becasue the is a small leak now inside that enclosure with the subsequent results.

The performance of the heater indicates low coolant level. Pretty strange about the multiple water pumps, but if is is under warranty, you need to keep going back to the dealer. They must be missing something...

Its the heater core you smell it on the inside because the fan is blowing it into the vehicle antifreeze is unuswal stuff it forms a mist and becomes air borne even a small leak you will smell with the fan running look for wet spots on the carpet under the core but the mist may be so fine and you wonn;t feel it but this your problem

there,s a chance that your hot-cold air trap is not working

Check both heater hoses under hood to see if they get hot, if they do the heater is fine. need to check to see if the selection doors inside the unit are opening and closing.