[Piotrsko]

thought about this for a while: I think the problem is that the CPU is looking for a tach signal which it won't get with the engine dead and not spinning. Obviously, empty cylinders/ engine compression during coast will act as a coast retard. So: your kill relay will need to add some sort of PWM signal to the ECU tach input that looks like the engine is running at some RPM at or above idle. the ECU should tolerate some stumble or momentary lack of signal, and with throttle off during the kill process just think it is coasting. I know the process in my F250 is: ecm doesnt care what rpm the engine is at during coast, it doesn't add fuel until idle drops to about 1000 rpm (because it "Romps"), taken from the TDC cam sensor. perhaps a 555 timer circuit running as an oscillator?