Heater pumps out cold air until the RPMs are higher than 2000. (No the A/C is not on) On cold mornings I'll go out and start my '05 Spectra5 and crank the heat up. I come back to it 1/2 hour later and its still cold air. I'll jump in drive away and as soon as the RMPs are up around 2000 or higher, bingo I got heat. BUT as soon as I stop at a red light and the RPMs are down cold air agian.... Whats going on?

On cold start up the computer is not looking at the air fuel mixture, only when it gets info from the ECT it then adjust the mixture. You have an exhaust leak under the hood somewhere. You may have the heater blowing at the same time bringing outside air in. This air has traces of the rich burning exhaust from the cold start up. Try turning the heater off until it is warmed up.

check blower motor resistor connector could be burnt or resistor it self

check the control module that opens the heater hoses tap. Check for air blockage in the cooling system that will not allow the coolant to circulate around the heater. Loose the highest hose and run until only coolant comes out . Refill the radiator.

a question to an answer: is your truck has any heat when you rev it 2000 rpm, or above?
have you check your coolant level? if level is low you have a small coolant leak, a water pump may be at fault, and causing air pockets in your heater core, check for leaks your self, dealer wont tell you if vehicle still under warranty.
good luck

That sounds like the coolant level is low. If it is not the use of "stop leak" has probably caused a partial clog which restricts the flow of water unless the vehicle is turning higher RPMS. While sitting still raise the RPMS to about 2000 and see if the heater blows hot air to see if the above mentioned problems are fact.

Low coolant,or water pump going bad.

Your likely problem is low coolant level. Check to make certain that your coolant level is topped up in the radiator and that coolant is also in the reservoir at the appropraite level as shown when on container when the engine is hot or cold. When the coolant is low, you have to have higher RPMs to get the coolant to pump through the system and heater core.

check the anti-freeze level in rad if *** is low in the rad it will cause this , in the raditor not the fill bottle as sometimes the fill bottle will be full ,***** be sure to do this with the engine cool and motor off

Just finished fixing my daughters 1999 taurus heat. It would blow warm only when running down the road. At idle it blew cold. I started with replacing thermostat, and water pump because they are the easier fix. Still did not help. Then I replaced the heater core. A daunting job but not that hard to move the dash slighly out of the way to replace. There is a good write up at tarusclub.com. After that, heat was better but at idle, it would still blow cool sometimes. Researched and found answer. Park car on the steepest hill you can find with front of car up. Start car and take off reservoir cap. Let car warm up and keep rpms about 1500. After a while the fluid will come running out of the car and all over the place but it will bring air bubbles with it. Reduce rpm, add more fluid and repeat about 3 times. It will make a mess but after that, the heater works perfectly. We get heat long before the temp gage indicates any and it never blows cold unless you lower the temp.