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Engine tries to start for a few seconds, then stalls

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by landspeed, Aug 3, 2024 at 11:23 PM.

  1. landspeed

    landspeed Active Member

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    I tried to start my 2007 Prius today, without success. The engine is doing a specific pattern of ‘trying to start’ / shuddering, and wondering if it might narrow down where to look?

    When powering the car up, everything seems normal, the engine spins up as normal for about a second, but the shudders, as if about to stall, for maybe a second, then spins normally for a second, then shudders for a second or two, before cutting out completely, with red triangle etc.

    I was suspicious it could be the DC12V output from the inverter, because I jumpstarted the car (the 12v battery is drained, and I have jumpstarted it using the replacement battery a few times … I will fit the replacement once I figure this out). However - before pressing the power button, the car displays will shut off if I remove the jumpstart battery, but after pressing the power button, I can remove the jumpstart battery, and the electric windows, headlights etc work fine (from the DC-DC 12v inverter), until I power the car down.

    I will pull codes once I find my OBD2 stuff, but am wondering if the above symptoms narrow down troubleshooting at all?
     
    #1 landspeed, Aug 3, 2024 at 11:23 PM
  2. rjparker

    rjparker Tu Humilde Sirviente

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    I would fit the replacement battery first. A really bad 12v battery can seriously drag down the system.
     
    #2 rjparker, Aug 4, 2024 at 12:28 AM
    Brian1954 and landspeed like this.
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    As your car runs, over many months and miles, certain parameters for the engine change, just from wear and tear, carbon buildup, etc. These changes are "learned" and adjusted for, by the ecu and sensors. When 12v power goes away on a Gen 2, the ECUs go to a factory default condition and all the "learned" values are lost. One of the "values" that will cause the engine to not start is throttle position. Carbon deposits tend to build up in the throttle body and over time, it causes the throttle blade position to change, but the car 'learns' it, and all is ok. Until it gets un-learned, like on a loss of 12v power. I have run into it a few times on jobs. Best solution for this circumstance is to thoroughly clean the throttle body and plate to ensure it is returning to its "as new" position so it matches what the ecu has defaulted to. Clean the MAF sensor while you're in there. Install the new 12v ASAP. You don't want to be jump starting the car frequently, as that is going to end up leaving you stranded at some point.
     
    #3 TMR-JWAP, Aug 4, 2024 at 12:32 AM
    Brian1954 and landspeed like this.
  4. landspeed

    landspeed Active Member

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    I will check the throttle body / MAF sensor (and will be very careful especially around the MAF sensor!)

    One weird thing is that (I know it isn’t good to do this) - I was disconnecting the installed 12v battery when not in use for a while, so it was always starting without any pre-existing memory data. It does sound like a throttle body from the symptoms, but I am worried I caused a power spike around the system when jumpstarting (because I use one of the strut bolts as the negative terminal, and it has light corrosion, so does spark a bit when trying to get a decent comtact ). Another odd thing is that I just checked some of the fuses, and the Battery Fan fuse was blown (and I know it was working a few days ago), and the ETCS fuse was blown (I am assuming the ‘TC’ stands for Traction Control, not throttle control ). I put a spare in the Battery Fan fuse (it didn’t blow again), but the ETCS is empty still (I’m using my 2003 Prius so I can take a few days to figure this out if needed)
     
    #4 landspeed, Aug 4, 2024 at 1:41 AM
  5. Tombukt2

    Tombukt2 Senior Member

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    Sounds like when you do get around to finding and reading your codes which should be of the highest priority at this point you're going to have the sale to start code and or engine runs terrible code for whatever it is maybe some misfire codes if it's in fact missing while it's trying to start anything with the 12 volt should be dealt with there should be no question about 12 volts and computer booting and what have you whether you're taking the battery in and out all the time or not It's kind of irrelevant If the battery doesn't have 12 volts in it standing wherever it's standing then it's not a 12 volt battery It was but it isn't now without 12 volts with the proper amps behind it you basically have nothing You can have 12 volts and pretty much no amps behind it so that the minute you try to use the 12 volt to do anything significantly with it it plummets to zero and fails when you put your test meter back on it it shows 12 volts but it's 12 volts with nothing behind it as soon as you try to put a small light bulb across the terminals it flickers and starts to die so therefore the 12 volt is no good and your car probably will not start.
     
    #5 Tombukt2, Aug 4, 2024 at 9:02 AM
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