Random Engine Shutdown/Low Power

Discussion in 'Gen 2 Prius Main Forum' started by BuckleSpring, Apr 11, 2026.

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  1. BuckleSpring

    BuckleSpring Member

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    IMG_20260417_182923_392.jpg

    Ordered 1-4, left to right. Nothing particularly weird, usual small amount of residue from oil burning as to be expected, but not bad considering they're ~50k miles old (If I'm remembering correctly).

    As for mileage, it's part of the 299,999 club, probably around 320-330k if I had to guess.
     
    #21 BuckleSpring, Apr 17, 2026 at 6:56 PM
  2. Brian1954

    Brian1954 Senior Member

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    Thank you for the picture of the spark plugs and the car mileage. What brand and type of spark plugs are they?
     
    #22 Brian1954, Apr 17, 2026 at 7:34 PM
  3. BiomedO1

    BiomedO1 Senior Member

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    2-4 looks a bit ashy, so burning lean. FWIW; they should look closer to #1; but it could just be the lighting of the picture. Are those plugs iridium and are those electrodes edges supposed to be rounded like that? I don't see the wire, unless they just put a drop of it on the electrode tip. I'm used to seeing a small iridium wire sticking out.
     
    #23 BiomedO1, Apr 17, 2026 at 7:35 PM
  4. BuckleSpring

    BuckleSpring Member

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    They're Densos, I couldn't tell you the PN#, my brother changed them 50k+ miles ago when he was borrowing the car for a couple of months.

    It's just the lighting, they're all identical in person.

    Either way, I don't get a change in misfire count in the live data at varying load/rpm, so I don't think the plugs are the particular cause of this issue.
     
    #24 BuckleSpring, Apr 17, 2026 at 9:19 PM
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  5. dolj

    dolj Senior Member

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    To my eye, that gap is too large. For 50,000 miles, those plugs look burnt out, so I wouldn't be surprised to learn that the 'iridium' tips were not iridium.

    I've pulled real Denso iridium tips after 100,000 miles, and the length of the tips looked almost new. I checked them, and they were still in spec. You need to check the gap with feeler gauges, they should be 1.0-1.1 mm, max 1.2 mm (I can't remember the old units off the top my head, sorry.)
     
    #25 dolj, Apr 18, 2026 at 12:04 AM
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  6. BuckleSpring

    BuckleSpring Member

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    No clue if they're iridium or not, but I agree with you that they're probably not judging by the electrode. However, I swapped them with some other plugs I had on the shelf and it made no difference to the engine running condition.

    I have it on the lift and I'm going to drop the exhaust out this evening to see if it's a catalytic converter issue.
     
    #26 BuckleSpring, Apr 18, 2026 at 6:26 PM
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  7. BuckleSpring

    BuckleSpring Member

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    I undid the flange up by the cat inlet and laid it down on the subframe, so I could take it out for a little drive around the farm for a test.

    Power went back to normal, didn't fall on its face or try to die. So... Looks like one of the cats has a restriction, and I'll deal with "fixing" that this weekend.

    Still no clue as to why this would lead to the lean code or the engine failing to start, but I'll take care of this and see if it returns in the next week or so.
     
    #27 BuckleSpring, Apr 20, 2026 at 11:01 PM
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