ICE runs rough as is shuts down

Thanks for the explanation, Daniel. I just noticed it yesterday again. Drove to a theme park and on the way back of course started out from the parking lot. Very busy, so some 20 mins of creeping along. The first 30 secs the engine was on to warm itself, then it shut down. Then I 'cleared' the parking lot and got up to speed: 80 - 100 km/h. Didn't really have to stop, until some road works caused the traffic to come to an almost standstill. Lots of creeping along again (almost all electric). The engine acted as if in S4. After the roadworks I was able to drive between 100 km/h and 120 km/h until I reached the city I live in. Past the traffic lights without having to brake (if I remember correctly), but had to brake at the roundabout and then the engine seemed to be back in S3.

So, even though I think the engine was warm when I entered the traffic jam, perhaps it had cooled down enough to go back to S3 and stay there because I came back up to speed without stopping 5 to 10 secs?

EDIT:
Funny thing is, because the engine keeps running (without showing it on the energy monitor) I get into green bars which in itself isn't that bad, because then I can drive a bit longer on electric, but to me it seems like a waste of petrol, hurts my mileage and hurts the environment. Perhaps the Toyota engineers need to think of another solution for warming up the engine.

 

I believe (though I cannot prove it) that when the battery goes above 6 bars, it becomes reluctant to accept more charge, and a significant part of the energy produced by the ICE is lost. If you are going faster than about 35 mph, you'll get into S3b and the car will sometimes go electric to draw down that charge. Alternatively, if you have a long enough stop and get into S4 it will do the same. But if you are driving below the S3b transition speed you are stuck, and wasting gas.

This is precisely the situation when I think the EV switch is useful. Soon after reaching 6 bars I use the EV switch. I do not try to drive far in EV. As soon as it hits 4 bars I disengage EV and let the ICE run again, unless I am in very low-speed traffic.

 

actually that is normal battery operation. the closer to fully charged it gets, the less charge it is able to take. that is the basis for all chemical reactions.

 

I feel this rough idle too. And my dealer also didn't notice.
As I read this thread, the unburned gas idea makes good sense. I'm coming to accept this as normal. Then I wonder if we're all experiencing pre-ignition. Has anyone tried 89 octane gas? Comments anyone?