I've got a 1989 300se which I just bought for $2K. Everything works on the car and the car is in exc. shape with no rust or damage. My only problem is heat. I have heat just so long as I don't touch the gas. If I am in idle and have heat, the minute I step on the gas, I start to lose heat till it blows cold. I have to stop the engine and restart in order to get the heat back. It will blow hot air so long as I do not step on the gas. I am able to coast forward in idle and have heat. Does anyone know what could be the problem? Thanks!