Originally Posted by
JojoJaro
Look, I have hundreds of hours of EFILive logging data that shows this. If you can download the EFILive viewer, I can send you some of my logs and you can see for yourself. I have captured many other parameters like Vehicle speed and throttle position. You can verify what I'm talking about. (Alternatively, if you are ever near Knoxville, give me a shot and I can bring you around town with the logging turned on.)
While coasting, the engine is being rotated by the momentum of the vehicle. That is why, the vehicle eventually slows down much faster than can be attributed to wind or friction, etc. This is how 'engine breaking' works. The truck is slowed down by the effort it has to do to compress the cylinders. While coasting the fuel will cut out and then as you slow down to a certain speed, the engine will resume 'idle' mode and start supplying fuel again. That is why it does not die.
It is a relatively simple matter for the ECM to know if you are coasting or idling - vehicle speed is the primary input. If your throttle position is zero and you are above a certain speed, then ECM decides that you are coasting. As you slow down further and reach the low speed cutoff, the ECM decides you are idling. Very simple. I can see this in my EFILive logs.
I am 100% sure, no fuel in being supplied to the cylinders when coasting.