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Mild case of Big Hand Syndrome?

Discussion in 'Generation 1 Prius Discussion' started by hybridtwins, May 6, 2012.

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  1. hybridtwins

    hybridtwins Member

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    All,

    In the last few years, my 2002 seems to have developed a mild case of BHS when starting the car on cold mornings. It kicks in at around 45MPH, but only seems to last for 2 or 3 blocks of driving... after that she settles down.

    Is it possible to have BHS only under certain conditions?
  2. tochatihu

    tochatihu Senior Member

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    There have been previous reports of this happening intermittently. Based on only what you have written, you should also make sure that the throttle air intake and butterfly are clean and working correctly.

    For the accelerator pedal assembly, top dollar is buying new. I'll let your shop quote the price but guessing $USD 400

    Next down is getting a rebuilt one swapped from Bob Wilson. he does not post here any more but I'm sure you can locate him

    Next down is doing the rebuild yourself. I posted detailed instructions on that years ago

    Finally is getting one used from any source including junkyard takeout.Obviously you would not have a guarantee uless you negotiated for one.

    Always nice to hear followup/final reports on these matters.
  3. northwichita

    northwichita .

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    Looked up 'Big Hand Syndrome' and found on the web this explanation of the phrase which I hadn't heard before.....
    ........prius slowing down. ......... 2001s and early 2002s used a resistive throttle position sensor that often became intermittent. In mid-2002 Toyota changed to a Hall effect sensor unit that was much more reliable. When the old ones failed it produced what came to be known in the Yahoo! Prius group as "Big Hand Syndrome" because it felt like a big hand had grabbed the car.
  4. 3prongpaul

    3prongpaul 6 Gen1s, 3 Gen2s

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    A sick/dying traction battery will also feel like something is holding the car back. Does the SOC (state of charge) on the MFD change rapidy? If so your battery may be dying.

    Try going in reverse (which doesn't use gas engine) and see how it feels and note what the SOC display does.

    A crappy battery will "turtle" after a few hundred feet going uphill in reverse.

    It should accelerate pretty quick....and for those of you who have a "good running car" go uphill in reverse and see how it performs...then remember your results to have a baseline to compare in the future if you ever have problems.
    2 people like this.
  5. hybridtwins

    hybridtwins Member

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    Well, I picked up my 2002 in November of 2001, so I guess that makes it pretty early. Can the Hall-effect design be retrofitted to my car?
  6. tochatihu

    tochatihu Senior Member

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    @5 I cannot answer that. I only saw the potentiometer versions of the accel pedal.

    Even if they are plug-compatible, I would not be certain that the associated ECU responds equivalently to the Hall effect signals.

    Hope that northwichita knows...
  7. everybody

    everybody Junior Member

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    I just stopped in to see the new format and noticed this thread. You're right, I don't hang here but I did post a revised method to "burn out tin whiskers."

    GOOD LUCK!
    Bob Wilson
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