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Discussion Starter #1
Well 'hard' might be a bit too strong but... I've had the black #7 2004 for just over a week and have about 250 miles on it. From the 1st drive home from the dealership I've thought that the transitions form the ICE to the electric engine and back have been pretty noticeable. I never miss one... from shutting off to turning on to switching, I can always feel a slight shudder or thump from the engine. Sometimes it is louder/stronger, sometimes it is quieter/softer but it is always there. From reading posts here is seems as if some (maybe most?) people have no transition noise at all, so I'm wondering if something is wrong with mine. Are the various engine transitions supposed to be seamless and silent?

Also, the yellow 'Engine Check' light came on today so I've got an appointment to bring the car to the dealership the day after tomorrow. They say it probably just needs slight "reprogramming" but I'm wondering if I should take up the issue of the hard transitions with them as well.

Thanks, JRjr
 

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nahh, i can feel mine too, and usually hear it...

Its the worse in stage1 of the startup procedure. Once the car has warmed up, its not nearly as noticeable...

I can usually only feel it when taking off from a standstill after its warmed up
 

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As for the shudders... your car is perfectly normal. As for the light, it is common for the check engine light to come on within the first couple hundred miles.

Don't take your car to the dealer any more than you have to; you'll not only waste your time there, some mechanics are just now starting to work with these cars. You don't want them to experiment with your car.
 

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Take your car in. It's probably just the O2 sensor detecting the burned coating from the catalytic converter, but they'll check the code to make sure and re-set it.

The slight shudder is normal. Sometimes it's stronger than other times. They've made it as seamless as they could, but everyone has it. Some people are more sensitive to it than others. You'll get used to it.
 

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Engine shut off will become smoother over time.

I noticed a huge difference between my 60,000 mile Prius and the brand new one. Then by 7,500 miles, the new one had become quite broken-in. The shut off had grown much more like the older Prius.

Give it time... well actually, miles.
 

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I definitely notice it the first time it kicks in after start-up, especially if I'm still stationary. I've also noticed it (more heard than felt) at low speeds.

Specifically, I notice the the transition when the ICE fires up. I don't tend to notice as much when it stops sparking.
 

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Discussion Starter #8
In case anyone was interested the problem with the Check Engine light coming on was diagnosed as:

TSB EG3005
Verification of Oxygen Storage Capacity

The Service Manager said that "most" of the new Prius they are getting have to have this worked on in the first few weeks of ownership. He described the work as a "recalibration" of the computer, not a software change. It took them about 1 hour 15 min to fix it.
 

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Since reading this thread I've been paying more attention to the shudder. If the ICE shuts off at a stop sign in S2 or S3 the shudder is quite pronounced. Once the car is in S4 (full hybrid operation) the shudder when the ICE starts or stops is very slight, less than a hiccup. I've got around 5,000 miles on it.
 

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RSnyder said:
S2, S3 and S4 are 2004 terminology?
I suspect (but do not know for sure) that they also apply to the Classic; and they may go under other names as well.

In Stage 1 the ICE is cold and will not shut off unless you turn off the car,

In stage 2 the ICE is a bit warmer, and in Stage 3 warmer yet. In those stages the ICE will shut off under certain circumstances, which I do not fully understand.

Stage 4 is full hybrid operation. The ICE must be at operating temperature and you must have stopped for 5 or 10 seconds (or have exceeded a certain speed, but I've read conflicting info regarding this.)
 

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RSnyder said:
S2, S3 and S4 are 2004 terminology?
Daniel said:
I suspect (but do not know for sure) that they also apply to the Classic; and they may go under other names as well.

In Stage 1 the ICE is cold and will not shut off unless you turn off the car,

In stage 2 the ICE is a bit warmer, and in Stage 3 warmer yet. In those stages the ICE will shut off under certain circumstances, which I do not fully understand.

Stage 4 is full hybrid operation. The ICE must be at operating temperature and you must have stopped for 5 or 10 seconds (or have exceeded a certain speed, but I've read conflicting info regarding this.)
FWIW, I've read in other posts that an odd ICE shut down sensation may be attributable to the engine settling into its optimal re-start position. In other words, it's supposed to do this. I don't know if this is accurate or not.

Drive happy,
Moo :)
 

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And yet it seems less noticeable when it happens when the engine is warm.
 

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Ok, well I haven't heard specifically of stages for the 2001-03 Prius. But there are a few similar behaviors.

When the engine coolant is below 50° C, the blue thermometer on the dash will light. It's very difficult to get the engine to shut off in this condition, though it can sometimes be done by hard acceleration in reverse. There are a couple hysteresis set points which control engine run for warm-up purposes. In P, the engine will run to warm up to 80° C, then shut down if not needed, until it cools to 60° C. I believe the upper set-point is lower when in D, but I haven't measured it. It also appears that the thermostat is fully open at 85° C as it's very hard to get the engine hotter than that, but it reaches 83° C quite readily even under light load.

Does the 2004 Prius exhibit similar behavior and do your 4 stages correspond? Could the hysteresis explain the stage 2 and 3 shut off conditions you don't quit understand?
 

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Unfortunately, the 2004 does not have a thermometer for engine or coolant temperature. So we have no way of knowing. That's one of my few complaints about it. The stuff about the stages or phases of operation has been posted here and there, possibly translated from Japanese technical manuals.

Here's what I've observed:

For a brief period after starting the car, the ICE runs continuously. Then it shuts off when there is no load or at stops. Then it seems to revert to being very reluctant to shut off, requiring a 10-second stop to shut off, except if you take it over 35 or 40 mph or so. To go into full hybrid operation (where it will sometimes propell itself under load with electric only and the ICE off) it must have come to a stop for 5 seconds, after being fully warmed-up, or have exceeded 35 or 40 mph, but in that latter case it will revert to stage 3 (no electric-power-only drive) after you've come to a stop, unless that stop was more than 5 seconds. Except that the EV switch (if installed) can be engaged, and the car driven in EV mode, without having met the criteria for S4 (full hybrid) operation.

Confused? I sure am! The above is what I think I've observed, and is not by any means intended to be authoritative.
 
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