Engine ticking noise that goes away...

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by priusesforever, Sep 30, 2025 at 10:23 AM.

  1. priusesforever

    priusesforever Junior Member

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    Greetings, I currently have an ad for two Gen 2 Priuses for sale here on priuschat. I've described and recorded a ticking noise in one of them in the ad. I've been monkeying around with the car some, put some sea foam in the gas tank and a little in the crankcase. I've owned various Gen 2's for over 18 years and have often wondered why the engine idle speed changes on it's own, sometimes shortly after startup. A couple of days ago while I was listening to hear if the sea foam was having any effect, I noticed when the engine "idled down", sitting in neutral, the metallic ticking noise disappeared. Is there any device that turns on or off , electrical ? mechanical ? when the engine is changing from some mode to another ? The noise sounds like it's coming from the left front top side on the engine, bay, as you're facing the car with the hood open. I'm at a loss as to what the tapping sound is. The only code my simple OBD reader throws is P0031. Thanks for any info or guesses.
     
    #1 priusesforever, Sep 30, 2025 at 10:23 AM
  2. ChapmanF

    ChapmanF Senior Member

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    I can't quite tell if you're saying that you sometimes hear, and sometimes don't hear, the ticking noise, all while in neutral.

    When you're not in neutral—in Park, say—there are indeed conditions that change. The engine can be actually idling, or it can be charging the battery: still running at roughly idle RPM, but doing up to around four horsepower of actual work, and you can hear the difference. The car shifts between charging and idling as needed for the battery.

    But it doesn't charge in neutral. Idle is always just idle then. So if you're saying you heard different things happening all in neutral, you've stumped me.
     
    #2 ChapmanF, Sep 30, 2025 at 10:57 AM
  3. priusesforever

    priusesforever Junior Member

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    Hello Chapman, thank you for that info and now I realize I mis - typed. The car was in Park not Neutral, I seldom put the lever in neutral. So, it sounds like I should watch the touch screen to see if the battery charging arrows and ticking noise are interelated.
     
    #3 priusesforever, Sep 30, 2025 at 2:16 PM
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