Recently I notice that my car heater wasn't working right. I have search the web for info on what could be the problem. The issue I'm having is when the car is in idle there's no heat but if I drive it and floor it i get heat but once I let go the accelerator there's no heat. I did change the thermostat and that did not helped the car would start to overheat needle would go pass the half mark on the temp gauge. I read on the web about the DCCV might be clogged up so I took it apart and clean it spray WD40 on it so it wouldnt stick and still no heat. I just change out the heater core and still no heat I notice that the car was staring to over heat with the heater core change out. Any tips would be helpful before I give up and take it to the dealer.