Replaced all 4 spark plugs and all 4 coil packs now having crazy issues.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Pinged, Apr 4, 2026 at 1:44 AM.

  1. Pinged

    Pinged New Member

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    Location:
    Michigan
    Vehicle:
    2009 Prius
    Model:
    Base
    Car was driving fine and no misfires prior to starting job. 296k miles.
    After replacing coils and plugs with NGK iridium from rockauto and Denso coils from eBay, I made sure all connectors clicked into place and added some marvel mystery oil to engine oil to help clean it up a little. on start up, the car made a loud rattling noise. Turned it off quickly and put the old coil packs and did an oil change Incase any carbon got loose and the rattling went away.
    Went for a test drive and it misfired then the engine turns off and the car started driving off the hybrid battery only.
    Scanned the car and recieved codes for
    -engine won’t start
    -engine not receiving fuel
    I’m thinking of reinstalling the old spark plugs Incase the new ones weren’t gapped properly or got the gap got damaged so the old ones can go along with the old coil packs back how it previously was and see if that will bring it back to normal. Any help or input would be appreciated.
     
    #1 Pinged, Apr 4, 2026 at 1:44 AM
  2. JC91006

    JC91006 Senior Member

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    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    The coils don't need replacement if they are working fine. And ebay stuff has so many counterfeits, it's probably not worth the gamble.

    In your case now, I would put all the old stuff back and see if things go back to normal. If it does, then visually inspect the new plugs to make sure none of them got damaged. It only takes 1 bad one to cause all your issues.
     
    #2 JC91006, Apr 4, 2026 at 2:16 AM
    xw20_driver likes this.
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