High RPM ICE idling: Cause???

For the second or third time, I've seen this morning an unexpected behaviour of the HSD for the ICE RPM.

Few minutes after I’ve left home, while the engine was still running to reach its operating temp and while I was neither breaking of accelerating (“glidingâ€, but with the ICE still running for temp reasons), the ICE RPM suddenly went up from its usual idle RPM.

I don’t have a ScanGauge to confirm the exact RPM, but its the same “toneâ€/RPM I hear when accelerating at the end of the HSI graph, just before it enters the PWR zone.

- Outside temp was -9°C
- This continued for about 5 minutes, then the ICE resumed to its normal idle speed.
- Using the regenerative or friction breaking had no effect on ICE RPM (ie it remained high).
- It felt like MG1 was spinning freely; fuel consumption being kept low at only 2.5L/100km (95 USMPG);
- As soon as I pressed the accelerator (from a stop sign or at any time) the ICE throttled down to its normal RPM and fuel consumption went higher to what I’m used to (between 5 and 10L/100km (50-25 USMPG)).

Is this a bug or a feature? Anyone else has seen this behaviour? Any idea on what’s happening?

On an old car, one might suspect a bad reading on oxygen, etc… but on a brand new car?...

 

Note: I was on flat ground.

As I remember, battery was "normally full" (ie with only one or two bars missing), but I may be wrong. I'll have to check this if it ever happen again...

So you're saying that the ICE was being turned at high speed by MG1? ... and there was fuel consumption as the ICE was warming itself up at the same time (to operating/heater temp)? Is this possible?

Yes, which normally keep the ICE on at low RPM.