Hi Scotty, i have 2003 sentra 1.8 engine. i changed thermostat and water pump ,heater wasn't working,was blowing cold air . Now it only blows hot when driving,cold when at idle or stopping at stoplight. i flushed the heater core in car and burped air with open cap , radiator is clean ,no crud when it was drained, no damaged fins,what have i missed doing? i have Haynes book, but limited info on 1.8 ,they cover the 1.6 and 2.2 engines more on cooling.don't think there is a temp coolant control valve,or i can't find it on my 1.8,please help. thanks

i'm here

it doesn't have a valve. Either your blend door system is broken inside the dash, or more likely their is air in the system (or heater core is just worn out, they will corrode inside and not dissipate heat well at low speeds then. )

thanks Scotty, i'll check it out tomorrow, yeah i was hoping not to get into heater core, but that looks like the problem.