That's basically what I saw today.
If I got off the gas completely, in 5th gear, above 32mph, the MPGuino would go to 0.00GPH ahd the scangauge would go into open loop. the fuel would start flowing again once it slowed down to 32mph and closed loop would be indicated.
It also seems to show "open loop" if I even look at the gas pedal the wrong way while accelerating
But there is not a significant jump in consumption between just below open loop and just above open loop. I guess I have to hook up the cheesey o2 monitor to see if the car computer is still checking the mixture or not.
But if I account for all that, and relight the engine with the throttle at an appropriate cruise condition (not decelerating, not over accelrating), it goes back to indicating closed loop within 2 seconds.