Car shudders

carleric · May 18, 2007

Every morning, after I start my car and drive to work, when I stop at the first light my Prius "shudders" and gives a small shake as it powers down. When the light changes, it starts up fine, and this shudder only happens once a day.

Is this normal? It doesn't seem like anything to be worried about, but I'm a new Prius owner and (more than a little) paranoid about treating it right.

ystasino · May 18, 2007

<div class='quotetop'>QUOTE(carleric @ May 18 2007, 09:46 AM) [snapback]444784[/snapback]</div>

Every morning, after I start my car and drive to work, when I stop at the first light my Prius "shudders" and gives a small shake as it powers down. When the light changes, it starts up fine, and this shudder only happens once a day.

Is this normal? It doesn't seem like anything to be worried about, but I'm a new Prius owner and (more than a little) paranoid about treating it right.
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If you are referring to normal engine turning off, the shudder is much more noticeable with a cold car... This what I interpret as a once a day to mean.

Earthling · May 18, 2007

My Prius does the same thing.

Engine shut-down is most noticeable the first time, when the engine is just barely warm enough for a shut-down. Later, when fully warmed up, it is much smoother and less noticeable. I don't worry about it.

Harry

brick · May 18, 2007

Normal, no big deal. It's probably burning fumes from the EVAP cannister or something.

hill · May 18, 2007

Welcome to P.C.
The search tool is a wonderful thing. You type in shudder, and lo & behold ... BOOM oodles & oodles of the same topic! Over and over
Yep, it's normal. Funkie, but normal. Just pretend your Prius is feeling a little chilly & it just shivered.

ystasino · May 18, 2007

<div class='quotetop'>QUOTE(hill @ May 18 2007, 10:27 AM) [snapback]444820[/snapback]</div>

Welcome to P.C.
The search tool is a wonderful thing. You type in shudder, and lo & behold ... BOOM oodles & oodles of the same topic! Over and over
Yep, it's normal. Funkie, but normal. Just pretend your Prius is feeling a little chilly & it just shivered.
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Actually the search engine does work much better than most forum search engines I've used!

carleric · May 18, 2007

Oh, man. The search tool. I just noticed it. Yeah, that would have been a better way of going about things.
Sorry.

Neicy · May 18, 2007

<div class='quotetop'>QUOTE(ystasino @ May 18 2007, 10:30 AM) [snapback]444821[/snapback]</div>

Actually the search engine does work much better than most forum search engines I've used!
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I just asked the question last week too!!! I think it's something we all notice at first and get scared something's wrong with the car. Now if I had a nickel for every time it was asked.....

patrickindallas · May 18, 2007

Maybe your baby saw an H2 and was shuddering in revulsion.

jamarimutt · May 18, 2007

Get used to it. At 62,000 miles my car shudders just the same.

F8L · May 18, 2007

I believe that is the transition between Stage2 and Stage3a?

The stages

The Stages:
S1:
In Stage 1 the ICE is cold. If not prevented by use of the EV switch,
the ICE will start a few seconds after the car is powered On. Until
the system reaches the S1/S2 transition temperature, the ICE will run
continuously. This accounts for the anomalous observation of electric
regeneration or no arrows (coasting) at the same time as a low
instantaneous mpg reading. No power is being drawn from the ICE, but
it is running. Also in Stage 1 you will notice that battery power is
used for even mild acceleration. In Stage 1 the HSD prefers not to
draw power from the ICE if it is not necessary. You cannot enter EV
mode while in Stage 1.
S2:
When the system temperature reaches 40 degrees C. (104 F.) the
computer goes to Stage 2 operation. The original Japanese poster gave
more detail than I clearly remember, but it appears that in Stage 2
the ICE will shut off if it is not needed to provide power. At a
stoplight, in S2, the ICE will stop immediately and fairly smoothly.
However, the car will not go into golf-cart mode in Stage 2. It can
draw power from the battery or it can recharge the battery, but will
not use the battery without the ICE. I have not ascertained if you can
enter EV mode from S2. [Update: you can.]
S3:
When the system temperature reaches 73 C. (163.4 F.) the computer goes
into Stage 3a. In S3a the ICE will not shut off unless you come to a
full stop for 5 or 10 seconds. Paradoxically, it is more reluctant to
shut off than it was in S2, and in S3a it shuts off very roughly. You
will feel the car shudder. But once it does shut off at a full stop in
S3a, it will then be in Stage 4 operation.
Once the car is in S3a, if you reach 34 mph without having come to a
full stop for 5 or 10 seconds, the car will go into S3b operation. S3b
is identical to Stage 4, except that if you slow down below 34 mph and
apply the brakes, you will be back in S3a. In S3 you can engage EV
mode providing that you meet all the conditions for EV mode.
I have observed that at the full stop in S3a sometimes the ICE stops
after 5 seconds, and other times runs for 10 seconds before stopping.
I do not know what determines the difference. I have also observed
more than one rough shut-down in a trip, suggesting to me that perhaps
the ICE may sometimes stop roughly in S2, and may not stop immediately
when you let off the accelerator in S2. I repeat that I do not clearly
understand Stage 2 operation.
Coming to a full stop while in EV mode does not seem to trigger S4.
You must be in normal mode when you stop in order to enter S4 operation.
S4:
Stage 4 is normal, full hybrid operation. The Prius is most efficient
in S4. The car will go into golf-cart mode at the computer's
discretion. You can encourage it to do so by lifting your foot off the
accelerator pedal for a moment, and then pressing on the pedal very
lightly. This is known as "feathering" the pedal. Feathering does not
force the car into golf-cart mode, nor is it necessary for the car to
go into golf-cart mode. It merely encourages the car to do so a little
bit sooner than it would otherwise do on its own. The benefit of
feathering the pedal is questionable, since the computer is deciding
when it thinks Golf-Cart Mode is most desirable. Increasing the time
spent in Golf-Cart Mode may only increase the efficiency losses
involved in charging the battery and drawing power from it. On the
other hand, encouraging Golf-Cart Mode when the SOC is very high may
be useful, as it creates head room in the battery to accept charge
wheen needed.
Above 42 mph the ICE must spin, and will generally provide power. It
is possible for the ICE to spin without providing power to the car
above 42 mph, and this has been observed. But since the ICE is more
efficient at these higher speeds, Golf-Cart Mode above 42 mph (Super
Golf-Cart Mode) is unusual. So the maximum speed in EV Mode is 34 mph,
cutting out at a tiny fraction over 34 mph, and the maximum common
speed in golf-cart mode is 42 mph. You can go faster in non-EV
golf-cart mode than you can in EV mode.
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Car shudders

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