YIKES! Knock/slap on startup.

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Drewintoledo, Jan 12, 2016.

  1. Drewintoledo

    Drewintoledo Junior Member

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    My Prius has been sitting in the fridged weather in my driveway. It's Tuesday and the temperature is currently 18F. The last time I drove this car was two days ago on Sunday.
    I started it up a few minute ago and heard a HORRIBLE knock or slap from the engine bay. It alarmed me to the point where I wanted to run in and grab my camera but I tried listening to understand what it could be. At first I thought it might be a belt came loose and was whipping around hitting the components but it went away after about 30-40 seconds. It was so loud that I thought the neighbor two doors down who was shoveling snow could hear it.
    I will let it sit overnight and will definitely capture this on video in the morning. I have a feeling the noise will be back.
    Has anyone experienced this?
     
  2. bisco

    bisco cookie crumbler

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    snafu. cold soak start up, there are a million threads here. usually, it's caused by starting the car and shutting it down before the engine warms up, like moving it in the driveway. then starting it after it's sat in the cold for awhile. unburned hydrocarbons in the intake manifold.

    i wonder if they solved this on the gen4

    edit: also, if you shut it right down and start it again, it's usually okay.
     
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  3. Air_Boss

    Air_Boss Senior Member

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    Check the few reports on PC; it's variously characterized as an infrequent start-up rattle. If it happens again, take it in and ask the dealership to look at it and any codes that may be present. Most people who have experienced it (as I have), have only heard it once (as I did, on a cold morning in 2013 after moving the car in the driveway the prior evening, which briefly triggered the ICE before it was parked). Seems to be a cold shut-down/cold start phenomenon, but not a repeat or frequent enough phenomenon to worry about.
     
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  4. WilDavis

    WilDavis Senior Member

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    Sounds just like I feel each morning before I've had my first cup of coffee! :eek: ;)
     
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  5. Drewintoledo

    Drewintoledo Junior Member

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    Thanks guys. You nailed what happened. I started it up and backed it up about 15 feet and immediately shut it down to get it into the sunlight hoping the sun would assist the ice melt. I did that yesterday.
    I did search the forums for "rattle" but only snooped through the first 10 or so results which seemed to be related more towards interior rattles while driving. I'll keep looking around.
    Wildavis-maybe I should pour coffee on it in the morning?
     
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  6. WilDavis

    WilDavis Senior Member

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    Yup! Works every day for me! (Hot, strong, black, no cream, no sugar! …gotta taste of COFFEE (none of that vanilla, chocco-walnut, hazelnut whip, raspberry-ripple, bloody boutique-garbiage stuff!) ;)
     
  7. Drewintoledo

    Drewintoledo Junior Member

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    Amen brother love! I drink mine the same way. I call those flavored coffees "yuppie coffee".
     
  8. Raphael Muscarelle

    Raphael Muscarelle Active Member

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    Have you figure out what this is
    Posted via the PriusChat mobile app.
     
  9. bisco

    bisco cookie crumbler

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    starbucks?
     
  10. bisco

    bisco cookie crumbler

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    /
    but seriously folks, have you cleaned your egr circuit?
     
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  11. Raphael Muscarelle

    Raphael Muscarelle Active Member

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    EGR is important yes.

    But when I was working in a shop people would come in saying it was 1 thing becouse there sisters friends 1/2 cousins father's brother's friend had that problem. We would have to tell them that's horrible for them but let me find out what's wrong with this vehicle.
    We would have done alot of work that was not needed if we just replaced what people said.
    Probably why we were always busy even tho we had Zero advertising.
    Posted via the PriusChat mobile app.
     
  12. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    @Drewintoledo :

    How many miles? Is the coolant level stable in the reservoir?

    If you haven't, I'd recommend to clean the complete EGR circuit, Intake Manifold and ports, and install an Oil Catch Can.
     
  13. bisco

    bisco cookie crumbler

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    in many cases, the knock at start up is simply unburned hydrocarbons in the intake manifold due to incomplete warm up the previous start. this has been a known issue since 2010, and toyota redesigned the manifold and replaced quite a few under warranty, but it didn't help much, if at all.
     
  14. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    I think that intake manifold revision was to revise the EGR passageways, from four-into-one, to four-into-two-into-one, which I don't think makes a lot of difference: a stem-to-stern cleanout is still needed, EGR and intake.

    FWIW, I've heard that banging at start-up once, and it was after a previous cold-start and near-immediate shutdown. But I don't think "hey, just don't do that" is a real solution.

    My 2 cents, the EGR and PCV circuits are working in concert to gum/clog things up.The cold start scenario "tips" it over some threshold, but avoiding that scenario is not making the problem go away, just delaying the onset of overt symptoms.
     
  15. Raphael Muscarelle

    Raphael Muscarelle Active Member

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  16. bisco

    bisco cookie crumbler

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    will it pass smog? oh wait, you're in florida
     
  17. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    That's pretty much what happens if you do nothing. Plus, combustion chamber temps climb...
     
  18. Raphael Muscarelle

    Raphael Muscarelle Active Member

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    EGR is supposed to cool combustion temp yes at highway speeds is when it's supposed to be open.

    Now this talk about engine start up problems becouse of EGR would mean the EGR would be open during startup and or idle. Many cars we blocked off to eliminate that problem. But that was with steel block engines.

    I've been trying to figure out why blocked EGR would cause head gasket to blow out. I just can't see the correlation.
    Posted via the PriusChat mobile app.
     
  19. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    I'm kinda stumped too, so thought: what exactly does Toyota say? This is Toyota Canada statement, on a "Warranty Enhancement Program". I'd strongly suspect they're not showing all thier cards, they're a business afterall:

    Toyota has received some reports of a rough idle and/or tapping noise from the HV transaxle at cold start due to a sticking EGR valve due to excess carbon build-up.

    What a run-on sentence lol; I thought I was bad. I'm sure they spent a fair bit of time on the phrasing and choice of words. They want to appear responsible and caring, and cover their you-know-whats...

    They don't seem to mind being vague though: how do we get from "excess" carbon build-up, to "HV transaxle" having "rough idle and/or tapping noise"? What's the connection?
     
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