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Sudden Acceleration precursor?

Discussion in 'Gen 3 Prius Technical Discussion' started by summit123, Feb 22, 2011.

  1. summit123

    summit123 Junior Member

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    I was driving today and had just gotten off the highway. I was going at no more than 10MPH when I heard some high pitched sound. At first I couldn't figure out what it was and thought maybe it was some outside noise. It quickly got louder over the span of the next few seconds and then I realized it was the engine. I had the pedal barely down so was definitely in electric mode. I quickly glanced at my Scan Gauge and actually saw the RPMs go from 1200's up to 3400 in no more than 10 seconds. I have never had the car rev this high, probably just 2400s when I'm on the highway going 70's. By this time I was getting very perplexed and worried, and had my foot completely off the gas pedal. I immediately pulled to the side of the road and parked(hit the P button). The car seemed to go into park mode fine and then over the next few seconds the RPMs went back down to 992, and I made it back to the house no problem.

    I was installing HIDs over the weekend and had disconnected the 12V ground as I had used a relay. I'm pretty sure the HIDs were all connected correctly as I double and triple checked everything and the lights did work fine. This morning, when I first went to work, the car would not start. I saw a bunch of warning lights come on and stay on, and the car didn't move when I shifted out of park. I turned off the car and then restarted it and then it started up fine. There was a brief moment later on when I was driving to work that I did notice a brief period of the engine spontaneously over-revving(for lack of a better word). It was pretty much similar to what happened later on, but was much more short-lived.

    Anybody have any idea what exactly happened? I had also disconnected the ground a few months ago when I was replacing the HU, but none of this happened. Should I be bringing the car in to the dealer to have them review the car's black box? The whole time this was happening, the thought of sudden accleration popped right into my mind. I was extremely relieved that the transmission did not link up with the ICU at the time because then the car probably would have really taken off at that RPM.
     
  2. cwerdna

    cwerdna Senior Member

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    downhill?

    I can't speak to everything else but were you going doing a hill at the time or prior? If the battery is pretty full (SoC on my ScanGauge at somewhere about past ~70% on my 2nd gen), as you're slowing, the car will essentially kick itself into something like B mode where the ICE RPMs go quite high (yes, even possibly past 3400 rpm) while going down a hill. This will happen w/no foot on the accelerator and even a foot on the brake.

    This is presumably to prevent the HV battery from getting overcharged.

    I can repro this quite frequently now as I have to go down a fairly long downhill grade to get home.
     
  3. summit123

    summit123 Junior Member

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    Re: downhill?

    I was driving on a completely flat road at the time, with minimal displacement of the pedal as I was slowly crossing a busy intersection. There should have been no hybrid charging. As I did just get off the highway after going 20 miles at about 65MPH, the battery load was 3 bars shy of complete charge, which was not any different than usual for me.
     
  4. F8L

    F8L Protecting Habitat & AG Lands

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    Re: downhill?

    I've had something similar to this happen on my GenII when going downhill on a winding country road. The engine stayed around 2400rpm despite my not giving any throttle input BUT the car did not push or act as if it was accelerating either so I just continued driving. I've only experienced this once in 126,000 miles of driving the car but it may just be the first time I've noticed it. *shrug*
     
  5. evpv

    evpv Active Member

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    You should take the car to the dealer immediately. Most likely the EDR won't show any faults but it's important to make sure they note your description of the problem on the service ticket, otherwise it won't be in their system.
     
  6. revhigh

    revhigh MPG Enthusiast

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    LOL !! :D

    I'm not sure a Prius could 'really take off' under any circumstances.

    I always laugh when I read that story about that idiot that said his brakes couldn't overcome the incredibly powerful engine of his Prius.

    REV
     
  7. chich2000

    chich2000 Junior Member

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  8. Teakwood

    Teakwood Member

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    "Anybody have any idea what exactly happened?"
    How do you expect someone who was a thousand miles away to know what happened?
    Go talk with the service dept.
     
  9. bisco

    bisco cookie crumbler

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    that's it, i'm dumping mine today!
     
  10. David Beale

    David Beale Senior Member

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    Was the battery full of charge? If so, that was the HSD dumping energy by spinning the ICE with no fuel injected. It happens from time to time.

    Just to reiterate - NO Prius has EVER "suddenly taken off" without the accelerator pedal involved! Either caused by mechanical or electronic faults. This has been proven by two separate investigations by people who are supposed to be somewhat intelligent. Further, because the engine IS NOT directly connected to the wheels, the Prius WILL NOT take off if you don't want it to and don't make a mistake with the controls. The engine -may- rev up, but that will have minimal effect on the drive to the ground.

    So a floor mat may kill you if you're asleep at the wheel but not the Prius "ghost in the machine".
     
  11. qbee42

    qbee42 My other car is a boat

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    The OP stated:
    Clearly this is not a case of burning off excess charge.

    I worry about the recent tampering with the electrical system. Most likely this is some sort of weird one-time event, noticed by the OP because of the recent work, but it could be a real problem. I suggest close monitoring over the next few weeks. If you see it again, visit the dealer.

    Tom
     
  12. fuzzy1

    fuzzy1 Senior Member

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    You are seriously overstating the findings. They made it crystal clear that they were not proving anything, particularly a negative. Rather, with considerable searching and testing, they were finding no evidence to support claims of uncontrollable UA.

    They did find a tin whisker electronic fault in a Camry part, but it threw CEL codes, was easily controllable, and had other layers of protection remaining.
     
  13. uglymuddah

    uglymuddah Junior Member

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    What I still can't understand is why people tinker around with the car and then whine on the forums that the car is acting funny. Tinker, whine complain, guarantee, sue....? It's a lifestyle and not a good one....

    #1 Stop messing around with your car
    #2 If it acts funny before or after tinkering go see your Toyota dealer. They'll know best what to do...But that costs money....
    #3 Stop messing around with your car...
    #4 Drive with your right foot and your right foot only.

    Damn....
     
  14. evpv

    evpv Active Member

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    *And NASA didn't bother testing a Prius, just 6 old Camry's. :)

    I'm sure the OP will rest easier now. Don't bother taking it to the dealer. NASA personally tested your car and it's perfect. :rolleyes:
     
  15. evpv

    evpv Active Member

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    :confused:

    [​IMG]
     
  16. fuzzy1

    fuzzy1 Senior Member

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    While NASA's deep dive into the electronic throttle control system covered just 6 Camrys, all from complaintants, NHTSA's other reviews cast a much wider net.

    Based on complaints, they selected 58 vehicles to inspect in the field -- 19 Camrys, 8 each Corollas and ES350s, 7 RAV4s, and onesy-twoseys of other models. Two were Prii, but both accidents were low speed events too slow to trigger the event recorder and fire the airbags. One hit a curb, the other hit a parked car while trying to enter its own parking space.

    NHTSA also purchased 23 Toyotas for inspections and performance and functional tests. 11 were non-UA Camrys of different years and configurations, used as design references. 9 were UA Camrys purchased from complaintants. They also purchased one Corolla, ES350, and RAV4 from UA complaintants.

    After those tests, NHTSA then sent 6 of those UA Camrys to NASA. So while NASA itself tested on only 6 Camrys, 'The Gummint' inspected and tested much more.
     
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  17. summit123

    summit123 Junior Member

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    Again, the SOC was 3 bars shy of a full charge. I have had the battery at this level many, many times and this has never happened. I have even seen the SOC at 2 bars shy of a full charge and also not had this happen. If the battery is full I don't see why the system would just temporarily halt the charging system by uncoupling instead of needing to do an actual "dump". If it really did need a dump then wouldn't that mean the system is not working properly and overcharging the hybrid battery?
     
  18. summit123

    summit123 Junior Member

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    It is standard practice to disconnect the ground when working on any electrical equipment, for personal protection and also for the equipment's protection. I'm sure any electrician or car technician would agree with that. That was exactly what I did when I was working on the car. So tinkering, yes, but messing around, no.
     
  19. evpv

    evpv Active Member

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    Careful fuzzy, if you keep reading the studies you might learn something that you don't want to learn.

    You might get a chuckle out the "comprehensive" study the NHTSA did regarding Audi's Unintended Acceleration problems. Yes, the same report that fueled the "driver error" excuse for the past few decades.

    NHTSA Study: "An Examination of Sudden Acceleration" Jan. 1989 | The Center for Autosafety