1998 Taurus Heater

My heater only blows warm air, when driving down road. When idling or at stop light, goes cold. Both heater hoses are hot. Radiator hose hot. Even tried new 154 degree thermostat, same deal. Can anyone help?

180 degree thermostat will let the motor get warmer, and provide warmer water to the heater core.
Check the blend door. It may not be opening fully.
Check the air intake. It may be partially clogged with leaves or other debri interferring with the blower fan.

I replaced my steel heater lines runnning up the firewall with Gates rubber heater hose and Gates connectors and elbows to replicate the steel lines running into and out of the heater core. That seemed to be the real problem for me, I did flush the heater core at the same time I replaced the lines. I still have great heat and it was well below Zero here today!!!! I have a 1999 Taurus and the Ford dealer flushed my system including the core twice last year and it did help some but didn't get the heat as warm as I thiught it should be. Late this fall I decided to flush the heater core myself and the steel lines were rusted so I flushed the core and replaced the steel lines with rubber and WOW what a difference, the heat has been great. My heat now measures 170% coming for the front window defroster. My Ford dealer could only get the temp up to 140% from the defroster....
Hope this helps, let me know if you try it and it works for you...Ed

My heater only blows warm air, when driving down road. When idling or at stop light, goes cold. Both heater hoses are hot. Radiator hose hot. Even tried new 154 degree thermostat, same deal. Can anyone help?

SOUNDS LIKE THE BLEND DOOR ACTUATOR, 60 DOLLAR FORD ONLY PART AND FAIRLY EASY TO REPLACE, IT'S JUST BEHIND THE RADIO AND ASH TRAY

I replaced my steel heater lines runnning up the firewall with Gates rubber heater hose and Gates connectors and elbows to replicate the steel lines running into and out of the heater core. That seemed to be the real problem for me, I did flush the heater core at the same time I replaced the lines. I still have great heat and it was well below Zero here today!!!! I have a 1999 Taurus and the Ford dealer flushed my system including the core twice last year and it did help some but didn't get the heat as warm as I thiught it should be. Late this fall I decided to flush the heater core myself and the steel lines were rusted so I flushed the core and replaced the steel lines with rubber and WOW what a difference, the heat has been great. My heat now measures 170% coming for the front window defroster. My Ford dealer could only get the temp up to 140% from the defroster....
Hope this helps, let me know if you try it and it works for you...Ed
IT SURE DID , WORKS 100% BETTER, I SAY THIS ONLY AFTER REPLACING THE HEATER CORE AND THE BLEND ACTUATOR FIRST, LOTS OF WORK BUT NOW WORTH IT, THANKS