Just swapped a D16Z6 auto tranny into a 92 honda civic hatchback 1.5L D15B7 auto tranny. D16Z6 installed and runs. My problem is when the car is started it idles fine but after sitting and heating up the engine will start to idle bad. The engine revs up and down sounding like its gunna shut off but it stays on. The valve cover is pretty hot and the hose from the radiator to the engine block is also extremely hot. The radiator fan turns on. Anyone have any ideas?

 

Check your coolant. Then check the iacv