No heat when first starting at idle. Will not blow hot no matter how long it sits or how fast it idles. Heat starts after I turn a corner, leading me to think it is a door in the duct.
But...
If I stop it stops blowing hot until I rev it up. Sometimes this does not work.

Anyone else having this problem ?

Make sure the cooling system has been bled of all entrapped air. There are at least two bleeder screws. Fill the radiator and fill the coolant reservoir with the appropriate coolant mixture, start and get the engine to temperature, and open the bleeder screws to release any air. You may have to vary the engine RPM while bleeding to purge all air.

Two? I saw just one at the thermostat... Where should the second been?

McLin, the other bleeder is at the point where the radiator hose goes into the block. That would be the other hose on the driver side.

Blue Bowtie;
Thank you for the info.
Could this also be why my temp gauge does not move ? Checked gauge, replaced sensor. When I turn on the key the gauge drops down a little also.

Problem could also be a vacuum leak in the control system.