2006 prius engine high revs stopped at stoplight

Is your 12V battery the original? Typical service life is ~4 years.

Have you ever had to jump start the car due "dead 12V battery?

Have you taken voltage readings, preferably after sitting overnight?

Was any of the following on"
air cond... setting,
defroster,
headlights?

You might look at this thread:
http://priuschat.com/forums/gen-ii-...call-alert-2004-2007-inverter-water-pump.html

 

Hi there. I have a Gen 2 2004 with 75k miles. I have had a couple of instances last year with the engine revving on its own but unlike your case, I was lifted off and cruising down a small gradient at high speed, around 75-80 mph on the motorway.

As I blipped the pedal the over revving eased and I can just continue driving it as normal. I think it's a normal case of engine braking at speed, but I can't say it's the same in your case since you are stopped.

Steven

 

Was your engine adequately warmed up when this happened?

I have 2005 Model. I have had this happen four or five times so far. RPM was around 2200 on most other occasions. Only once it was 3000+. Engine was warm on all occasions (170 F and above). It would not go off despite getting foot off. Once I was in parking lot when this happened. Only powering the car off stopped the engine. However other than engine revving up, car was always perfectly within control. Even with foot off of brake it would roll as usual.

http://priuschat.com/forums/gen-ii-...9887-ice-ran-high-rpm-no-apparent-reason.html

Would it be that with battery fully charged ( thus no electrical load on engine) and not much load on engine, it will just rev up to use whatever fuel is supplied in frictional load? Something like what would happen when you would press gas pedal in a conventional car while in Neutral or in Parking gear.

To me engine should have been turned off or fuel supply cut off which generally does happen. But like john1701a suggested in other thread it may be some house keeping event.

 

You state that the SOC was all green bars. My guess is that the ICE was spun up to bleed off the excess energy to protect the battery. This is normal.

 

ICE revving while stopped is not uncommon when you have full 8 green bar SOC. It's just dumping excess charge.

Getting full SOC on level ground is a little unusual though. So forget the revving that's normal, just concentrate on the SOC thing, that's the root cause.

 

This is most likely the correct answer. The engine does not actually run in this situation. It is spun as a load for MG1 - works as a big air pump - to burn off excess charge in the HV battery. You typically see this after a lot of regenerative braking, such as coming down a hill.

Tom

 

never seen anything like this in 6 years driving an 04 and 08. had 8 green bars plenty of times.

 

You were probably just under the trigger point where the ICE will spin up.

 

It takes more than 8 green bars. That's why it throws away energy, to stay at only 8 green bars.

I've seen it routinely on climbing trips out west. In Michigan we don't have enough vertical drop to get it, except under very special circumstances.

Tom

 

I've got a big hill with traffic lights at the bottom near here and if I start the descent with 6 or more bars SOC then it's usually 8 bars at the bottom and if I get the red light then the extra regeneration from stopping throws it into "spin out" mode every time. Funnily enough it often doesn't start doing it until after I've been stopped at the light s for a few seconds and then it starts dumping charge (spinning).

Lately if been deliberately trying to make it run in EV mode prior to when I get to this hill to knock a little bit off the SOC before I start the descent. Seems to be working pretty well as I haven't seen over 7 bars there for a while.

 

I will watch GPH and SOC on my scanguage next time it happens. At least once when it happened I had gotten down a 100 ft hill and then parked at bottom of hill. The problem happened when I started again.

I have had this happen when I was rolling down hills and when I saw SOC was full. That I fully understand, I would say car is using something equivalent of 'B' Mode.

But to get rid of excess charge, the motor would have to turn in opposite direction thus revving up engine further. Does Prius do that? GPH in this situation must be not consistent with RPM.

 

If you SOC was ALL eight green bars, you may have over-charged your battery. What happens is, in the Prius, when your battery gets to it's full limit, your engine will turn on and actually burn off electricity. (Prius like for battery charge to be between 20%-80%). So naturally, if your SOC goes over it's comfortable limit, the engine will burn off access electricity.

 

Oops, wrong thread....

 

Yep that's right, MG1 just spins the engine like it was a great big air pump and that's how it dumps any excess battery power.

Seriously it's not a problem. It really is normal behavior that is totally well known and well understood. Not everyone has personally experienced it because not everyone drives on the sort of terrain that's prone to giving 8 green bars SOC (and then some).

Yep definitely that's the thing to watch. As I said before that is the root cause, the engine revving is merely a consequence.

BTW. While it's rare to get full SOC on level ground (as it usually happens on large descents) I think it would be possible with fairly aggressive driving. I know that with lots of repeated acceleration and braking I can crank up the SOC. Normally when I'm driving on relatively flat terrain my SOC sits at 5 to 6 blue bars. But sometimes when I accelerate hard from a traffic light only to have to brake hard for the next set of lights and that gets repeated a few times then I get 7 bars. Has your driving style changed at all recently?