ICE short cycling at stoplight

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by James Luckett, Feb 27, 2015.

  1. James Luckett

    James Luckett Junior Member

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    My 2008 did a strange thing last night -- the ICE was short cycling at a stoplight. It would start and then immediately turn off, then immediately start again. It did this about 5 cycles. Cold night, coldish engine, heater on, recent repair from being rear-ended (5 days since got it back from body shop). 12V battery seems good (12.3 volts no load, car not in ready mode; 11.6V withheadlights on and car off). No purpose could be served by such short cycles. We turned off heater and then the light changed and we were rolling forward and engine short cycled one more time and then the behavior stopped for the rest of the trip. Anyone ever see this? Have a theory why? Don't recall it ever doing this before.


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    #1 James Luckett, Feb 27, 2015
  2. stonerider

    stonerider Member

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    Your 12v battery is almost 7 years old, 2-3 years more than expected service. 12.3v is low, 11.6v with headlights on is too low. Time to replace it.
     
    #2 stonerider, Feb 27, 2015
  3. James Luckett

    James Luckett Junior Member

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    Not 7 years old.

    I replaced the battery with an Optima Yellow Top last year. I read elsewhere online that 11.6V with headlights on is good. What do you get with headlights on? If 11.6 is bad, then battery was damaged in the accident. But I think it is not bad. I'm about to install a new Yellow Top in my 2009 Prius so I'll soon be able to run the test on that one and compare.

    See: Toyota Prius: How to Check the 12v Auxiliary Battery Health - PriusDIY.com

    "Test 2: Again, without your foot on the brake, hit the power button again. You just put a current load on the battery and it should be about 12v. Depending on your reading you may not want to proceed to put more load on the battery. If you turn on the headlights, rear window defroster and heater fan you'll start seeing the voltage drop. Elearnaid says about 11.3v is where you should be at with a new battery and 10.2v and less the battery should be replaced. I was in the mid 10v range so I decided to just replace it for a Yellow Top!"
     
    #3 James Luckett, Feb 27, 2015
  4. valde3

    valde3 Senior Member

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    Check the battery ground cable connection and other battery connections as well. If the area back there was painted you might even want to sand paint away from under cable connection (and then put something on top of it stop it from rusting). Mine had exactly same behavior before replacing the battery.
     
    #4 valde3, Feb 27, 2015
  5. Britprius

    Britprius Senior Member

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    The MFD readout is not always an accurate or should I say is unlikely to be accurate. As previously posted I have checked a number of gen2 Prius MFD displays against a calibrated volt meter.

    All of the displays under read to varying degrees, from 0.1 volts to 0.5 volts making the displays suitable for comparison use only. Alternatively check the display against a volt meter connected to the battery, and add any offset to future MFD readings.

    Even a difference of 0.2 volts is a substantial error as far as battery voltage is concerned.

    John (Britprius)
     
    #5 Britprius, Feb 27, 2015
  6. bisco

    bisco cookie crumbler

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    check the battery with a volt meter after the car has been off for a few hours. 12.5 or better is okay. you could try charging it to see how it holds up, before replacing. i'm not sure the short cycling is due to a bad 12v, but something isn't right.
     
    #6 bisco, Feb 27, 2015
  7. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    My Gen2 did this a few times and I just figured it didnt shut off in the right spot in the combustion cycle.
     
    #7 PriusGuy32, Feb 27, 2015
  8. Mylar

    Mylar Member

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    Mine does this every so often. I typically turn off the HVAC and let my foot off the brake, roll forward slightly, reapply brake and it goes away. It can't be the battery because I installed an Optima yellow top about 5 yrs ago and my car has done this since I've owned it.
     
    #8 Mylar, Feb 27, 2015
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