91' KA24DE cooling system problem.

[Sleep]

Ok so i just replaced my thermostat last year....and now it just started last week.....

when the car is moving, or idling the temperature gauge fluctuates from normal temperature all the way to hot. Sometimes it just sits on hot. The car is NOT overheating. When the temp starts to rise past normal level, my heater starts blowing cold air (its winter on the east coast). If it was really overheating it would blow hot.

Not only does my heat go out, but my idle shoots up to anywhere between 1000 and 1500.

Has anyone ever had anything like this happen to their 240?

I JUST got home from work after replacing the thermostat with a genuine nissan 1 hoping that would fix it....but it didn't

Any help is highly appreciated

[Structure240sx]

coolant temp sensor maybe? i really am not sure. but the 1000-1500 rpm could be it stuck in cold start mode. makes the engine run rich to warm it up faster.

[Sleep]

south jersery? Im right above northeast philly.

[Structure240sx]

yea im in sicklerville about 15-20min away from NE philly right off 42