ICE Shuddering in the Heat

mine was doing that too today in michigan as well...

Its a michigan conspiracy i tell you!

 

Sounds like the ICE trying to charge the battery. You don't want to shift into neutral with few bars left on the screen. just let the computers decide what's best for the system.

 

I had something similar on the freeway from Austin to San Marcos on Sunday. It was already crowded and slow from construction, but just cleared up when suddenly none of the 3 lanes were moving. Some people cut across the grass to the access road, but then they were barely moving too. The temperature was in the mid-90's. For a long while we moved anywhere from 2 to 4 mph--when we did get to move--about a car length each time. Got to a place where all three lanes were merging into lane one, and there were patrol cars of several varieties (DPS, sheriff) plus fire trucks and ambulance. Several uniformed officers were marking places on the highway in the lanes that were closed, but I didn't see any vehicles that I could tell had been in an accident. Turned out some guy had walked onto the rural freeway in front of a truck, so I was glad I didn't see the physical evidence. It took me about an hour and a half to get to my destination, 28 miles from my home.

Anyway, without a clue as to how awful the situation ahead actually was, I watched the MFD. We got down to pink bars in a pretty big hurry, and I was aware of that shudder down, start up pattern. I noted that even with the pink bars, the arrows went from the battery almost as much as to the battery. Though I felt a little nervous about it, I kept remembering all the advice on this site about relaxing and letting the computers do their job taking care of the car.

 

wow that is weird!!

i think if that had happened to me i would have tried turning the air conditioning off first (briefly for sure!!) to see if that kept the ICE from cycling like that.

last year when it was hot and i had the air conditioning going, there was a few times while sitting in traffic and i would be low on bars that i tried to rev the engine a little bit to charge the battery faster, but there was no response. always did this only in park. never tried any other gear. just as well, overreving might damage the battery more than help it.
the only time i ever got to pink bars was when i was doing more parking than driving one day on I-5 in 100º heat

anywat... just my 2 ¢

 

Actually I did turn the A/C off for a little while, Dave, until I remembered all the PriusChat assurances. And I had considered revving the motor, too.

Beth

 

I've had that happen a couple of times, and I just took my foot off the brake for a second and rolled forward a foot or so before re-applying the brake. Seemed to stop the car from doing the ICE start/stop loop.

It's strange that it happens when the battery isn't fully charged (that circumstance is normal for a slightly overcharged battery and is how the car runs-off excess charge). But like I said, it has happened to me too. Nothing to worry about however.

Dave

 

I have seen situations when the battery gets low because the AC is cranking from the built up afternoon heat, and the car was sitting at long lights and/or traffic, that the ICE stays running. I suppose the AC compressor takes quite a bit of energy at its highest speed, and ICE at charge idle can just barely keep up.
Sounds more efficient that way, once you think about it.

 

Dave... interesting you should say that about rolling forward. in situations where i will be stopped for more than a second or two, i put the car in park so i dont have to waste power illuminating the brake lights. maybe that is why i have not experienced that rapid start/stop cycle.

in cases of slow traffic i am rarely at a standstill as i always double my following distance to allow for coasting room so i still wouldnt have my foot on the brakes.

another observation i have noticed and this happens even when the car is cold. when i come to a stop light (there is one less than a block from my home) i put it in park and every time even in cold weather, the ICE stops immediately. i will start paying more attention to this as related to the SOC to see if this happens at a reduced level

 

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My totally unscientific "guess" is that the torque sensor occasionally gets fooled and thinks that you might be trying to go forward, or hold position on a hill. By rolling forward a few inches, it takes the "tension" out of the system and the computer knows it can really shut down the engine.

I can't quite explain it, but when I rolled a few inches forward, it stopped the engine cycling the last couple times it happened to me.

But it could just be coincidence. Regardless, it's not hurting anything if it's cycling, I was just curious if I could find a way to stop it .

Dave

 

well i have to say that Toyota engineers have done a great job with the Prius i find it hard to think im in a position to 2nd guess their decisions so i dont worry about it either. but it does take power to cycle the ICE up albeit a small amount i believe since they do make the engine easy to turn over

does anyone know how much power it takes to cycle up the engine? Frank get your scanner out and let us know if you can get enough info to give us the work used to start the ICE up