1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Accelerator pedal sensor... or not?

Discussion in 'Generation 1 Prius Discussion' started by VoltsNAmps, Sep 24, 2015.

  1. VoltsNAmps

    VoltsNAmps New Member

    Joined:
    Sep 24, 2015
    3
    0
    0
    Location:
    Maryland
    Vehicle:
    2003 Prius
    Model:
    One
    I bought my 03 Gen 1 about two weeks ago and since then I have recently noticed a problem with the accelerator pedal. I've read through the different posts, but can't seem to find anything relating to my problem.

    There seems to be an "overlap" (for the lack of a better term) when pressing the pedal. It usually happens after starting the car and driving in the morning, but I've noticed it happening at other times as well. When I accelerate to the speed I want to travel, say 25mph, I let off the pedal slightly to maintain the speed. However, I can't maintain the speed. The car starts to slow down. When I press the pedal ever so slightly to compensate and maintain speed, the car accelerates. In essence, I can't keep the car at a steady speed. It is either slowing down or speeding up. This didn't happen during the first week or so of driving it. It just started today. Any ideas? Is there a way for the ECU to re-learn the accelerator pedal range or something to that effect?

    As A VW mechanic for 10 years, VW's would lose the pedal calibration from time to time and the fix was simple... turn the key on, but don't start the engine... slowly press the accelerator pedal to the floor, then hold it there for 3 to 5 seconds.... then slowly release the pedal until your foot comes off of it. Turn the car off. That's it. It's calibrated.
     
    #1 VoltsNAmps, Sep 24, 2015
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,327
    15,111
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The G1 pedal just has a variable resistor, purely mechanical with a wiper that rotates over a resistive surface, and is known to get noisy over time. Sounds like yours has developed a sort of nonlinearity right around the spot where you would normally hold it at a steady speed ... maybe not surprising, because that is probably the spot where the wiper has rubbed the most all of its life.

    There have been a bunch of threads on here about opening it up and cleaning it. I haven't had to do that with mine yet. I did have to do the same thing recently with one of my heater servos but I think I had it easy ... the heater servo covers pop right apart. If I remember right, the accel sensor housing is glued or sonic welded or something, making it a pain to open and glue back together. But the old threads about it are more trustworthy than my memory.

    -Chap
     
    #2 ChapmanF, Sep 25, 2015
  3. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
    27,165
    15,409
    0
    Location:
    Huntsville AL
    Vehicle:
    2018 Tesla Model 3
    Model:
    Prime Plus
    I would ask you to try the cruise control which is effective down to 24 mph. The lowest limit is 23 mph but requires a dead-level road. The reason is if there is some sort of 'surging' going on, it should kick out the cruise control.

    Now the usual accelerator problem is also called "dead hand" describing the symptom. It comes from when the accelerator dual-pots disagree. Not knowing which is right, it triggers the car into 'safe home' mode and limits the speed to about 25 mph. If it happens in the field, a rapid series of accelerator operations, car off, can sometimes give a little relief.

    My current hypothesis is 'tin whiskers' which can be mitigated by using a 9 V battery to burn them out. I used to clean them following Doug's instructions. However, I don't offer that service any longer but will mentor folks on how to do it:
    1. Remove accelerator assembly.
    2. Use Dremel type tool to remove the thin plastic holding the gray top.
    3. Clean the interior and re-tension the wiper fingers.
    4. Re-seat gray top and use JB Weld or equivalent to seal.
    5. Reinstall assembly.
    BTW, I found one accelerator assembly that had a 'bent' arm on the sensor. It too had a non-linear response.

    Here is a list of my existing accelerator jpg files:
    public_html/prius/pri_acc_100.jpg
    public_html/prius/pri_acc_110.jpg
    public_html/prius/pri_acc_120.jpg
    public_html/prius/pri_acc_240.jpg
    public_html/prius/pri_acc_300.jpg
    public_html/prius/pri_acc_340.jpg
    public_html/prius/pri_acc_350.jpg
    public_html/prius/pri_acc_370.jpg
    public_html/prius/pri_acc_372.jpg
    public_html/prius/pri_acc_730.jpg

    Use "http://hiwaay.net/~bzwilson/prius/pri_acc_100.jpg " to see the images.

    Bob Wilson
     
    #3 bwilson4web, Sep 25, 2015
(You must log in or sign up to post here.)