Strange engine behaviour -- like revving while stopped at light

Use carb cleaner applied to a cloth and/or Q-Tips, not sprayed directly. Again, @NutzAboutBolts has a video, #14 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

 

I gotta say this doesnt register with me one bit. Would anyone have more info on this or history of where this explanation comes from???

If you hear the engine revving then there is combustion occurring. This proposed mechanism of burning off stored charge (especially while stopped at the light) makes no sense whatever to me.

 

It's a behavior I haven't personally seen ... I know the engine can be spun by the transmission to dump excess energy while the car's in motion (say, during a steep descent), in order to avoid overcharging the battery, though I've never personally seen it allow the battery to overcharge and then sit at a stop light spinning the engine to burn the excess charge off. My Gen 3 pretty much never lets the battery exceed 80% SoC (as shown on a ScanGauge, not the dash display, which is differently scaled). Its favorite target point is 60%, but if I ever happen to arrive at a stop light with a higher state of charge, I've never seen the car try to dump the excess while I'm sitting there; it just holds on to it, then uses it up as I accelerate away from the stop.

A little bit of 'engine revving up' sound can be normal at a stop, just before the engine shuts off. If the battery SoC is below 60%, the car may want to do some charging first, which puts a load on the engine. It will be running at idle speed, but with a slightly deeper note because of the work it's doing. When the car gets the battery charge where it wanted, it cuts off the charging load, which usually gives a sound of the engine note getting lighter and revving slightly higher, usually just before it then shuts down.

 

Same here. I've gone up to 79-80% soc about 3 times a month downhill for 10 minutes, ICE never came on to spin the excess charge.

 

Too many factors on variable revving/surging.
Maf sensor
loose / leakey injector O-rings.
egr stuck open
pcv valve intermittent
pinched and leaky vacuum hose
bad motor mount can add more feel on the vibration
list goes on and on...
more trouble if its not seen on trouble code..

PS I replaced my plugs not too long ago 120k miles. I manually flushed the injectors and replace seals. I normally have a bit of this surging. For some reason I don't feel it anymore and I was averaging 45mpg in the whole year. Now I have 46mpg. Hope it last with no surprises along the way.

 

I agree with cleaning the MAF and Throttle Body regualarly, like every 30-40k, especially as you hit high mileage. It will keep things running smoother and not show the dreaded red triangle that can be mis-diagnosed as a bad battery or ECM sometimes because of that. Yep had several dealers trying to get me to spend $3k to $8k to fix my car when a simple clean of the MAF and Throttle body was all that was needed. Gen 2 prius sold at 325k and still running great, current Gen 3 at 246k and chuggin along!