heat works when I accelerate

[alincosma]

I have a 2001 Grabd Am GT. This winter it started to have this problem when it would blow up hot air only when I accelerate, on iddling is blowing cold air( not as cold as it is outside but close).
Anyone has an ideea of what could be the problem?

Thanks guys.

[xeroinfinity]

Could be your water pump is going bad or you have a blockage in your cooling system.
As the pump fins rust off it take more rpms to move the coolant. A bad thermostat can do this too.

I would check the water pump first.
Then do a cooling system flush if one hasnt been done in the last 3 or more years and replace the thermostat.