my heater only blows cold air when idleing
Is your coolant level correct . . . ?!
RE: db4690’s remark
I agree. You may have air trapped in the heating system. Have you drained and refilled the cooling system lately? Changed the thermostat? Also a possibility is the heater control door may not be operating properly. Listen for an air leak under the dash on the passenger side.
Good luck with your search.