toyota prius gen 3 engine knocking solved

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Anas Al-Mustafa, Jun 7, 2015.

  1. Anas Al-Mustafa

    Anas Al-Mustafa Junior Member

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    I had a toyota prius gen 3 last year where it had an engine knocking sound, where i tried every TSB and changed the spark plugs, spark plug cables, intake manifold, engine knots..... etc nothing worked except the following video which solved the knocking completely with no return.

    i hope this helps anyone out there who did not benefit from the toyota TSBs to solve the engine knocking problem.



    It will be great if you guys try it and see if it works on all toyota prius gen 3 with the engine knocking problem.
     
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  2. bisco

    bisco cookie crumbler

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    welcome anas and thank you. is this the cold start knock that lasts for a few seconds?

    or is it knocking under load when driving? thank you.
     
  3. gliderman

    gliderman Active Member

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    The different spray angles show different levels of constriction in the injector. Any constriction is going to reduce the amount of fuel coming out of the injector and will give a different burn curve. I dont know what knock you are addressing with this demonstration. But as long as the correct amount of fuel enters the combustion chamber with the correct timing of the piston stroke and ignition fire, the engine should not knock no matter what angle the spray is introduced.

    So if you are saying that the different spray patterns or level of constriction is causing the knocking, then it is because of the variation in fuel spray volume(fuel to air ratio)and the resulting delayed timing of optimum combustion. However the engines various control units should automatically adjust to this situation.

    Just a guess.

    YMMV
     
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  4. Anas Al-Mustafa

    Anas Al-Mustafa Junior Member

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    Thanks bisco
    This is for the cold/warm start knocking that lasts for a few seconds when you first start the car then disappears. The engine knock appeared in cold and warm weather. My observation is that the fuel injectors will spray badly at startup then start spraying correctly when warmed up
     
  5. Anas Al-Mustafa

    Anas Al-Mustafa Junior Member

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    The problem with the injectors spraying fuel on different directions is that it will generate multiple sparks at different times especially at the edge of the piston where it will give an engine knock. once the car heats up properly and starts pumping more fuel then the injectors start working correctly (its just at the startup where the injectors spray badly then start spraying correctly when warmed up)
     
  6. bisco

    bisco cookie crumbler

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    this is a huge discovery anas, many. many people suffer from this problem, and even toyota hasn't been able to solve it. i just hope we have availability of injector service here. thanks again!(y)
     
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  7. Former Member 68813

    Former Member 68813 Senior Member

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    sorry Anas, but you need to read some more how engines work. the fuel is not directly injected inside cylinders in this engine and the "bad" spray pattern will not cause "multiple sparks".

    the cold start knock is simply a misfiring cylinder. i easily replicated that by disabling one spark plug.

     
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  8. bisco

    bisco cookie crumbler

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    are you saying one cylinder isn't firing during the cold start knock?
     
  9. Anas Al-Mustafa

    Anas Al-Mustafa Junior Member

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    Thank you, i really hope it helps others since it surely drove me crazy :)
     
  10. Anas Al-Mustafa

    Anas Al-Mustafa Junior Member

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    Taking one spark plug out will generate a similar problem but not the problem itself. Since i have replaced all spark plugs and spark plug cables to eliminate them out of the solutions and the car still knocked during startup in (cold and warm weather)

    If the problem was spark plugs or spark plug cables then the engine knocking would have continued regardless of the amount of fuel flow (knocking will occur on startup and while engine is running)

    The different angles of sprayed fuel will generate multiple sparks with very slight different timing because of their angle and position reaching the spark plug thus creating an non uniform spark around the piston especially on the edges where the piston knocks.

    This what worked for my car and wanted to share it. (Your car might be different)

    One more thing: My car was not producing any problem codes
     
    #10 Anas Al-Mustafa, Jun 8, 2015
    Last edited: Jun 8, 2015
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  11. Former Member 68813

    Former Member 68813 Senior Member

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    yes. probably due to condensed moisture/fuel due to previous short cold run. it can happen in a regular car too, its just it's more noticeable in this hybrid due to feedbacks between ICE and G/Ms.

    right, yours could have had a problem with injectors causing misfiring while cold.

    the only reason i got a code, the coil was disconnected and ECU saw a problem with lack of current in that circuit.
     
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  12. zmre2b

    zmre2b Junior Member

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    Have others solved the engine knocking problem with cleaning the fuel injectors as this video suggests?
     
  13. gliderman

    gliderman Active Member

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    I doubt it. Anas premise that the fuel injectors squirt fuel directly into the combustion chamber and onto the piston is not correct. Fuel is injected into the intake manifold for each of the four combustion chambers coinciding with the intake valve opening.

    Gasoline engines do not use direct injection, as far as I know, but there may be some. The Prius is certainly not one of them.
     
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  14. DJ Q

    DJ Q Junior Member

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    Hey all,

    Bumping this thread to confirm that this works.
    I had the same problem.

    I started getting this knocking noise mostly when the engine is cold. Noise started getting louder and my fuel economy was dropping. Went from averaging 23 km/l all the way down to 18 km/l. Instant KM/L on the highway was around 20. 23 at best.
    Started losing power, especially when going up hills.
    Thanks to this thread, I realised that this was the simple fix needed.

    When done, instant KM/L on the highway instantly shot up to 30km/l. Noise gone. Car even idles smoother.

    Hope this helps anyone having similar issues.
     
  15. alanwagen

    alanwagen Member

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  16. farmecologist

    farmecologist Senior Member

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    Seems like prudent use of Techron would also maintain the injectors enough to prevent something like this.

    Also, I think you will get some blowback on your assertion that this 'solves' engine knock. We are a skeptical bunch here. :whistle:

    At any rate, thanks for your contribution!
     
  17. ChapmanF

    ChapmanF Senior Member

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    Anything that causes misfiring can make a knocking racket from the engine, and the fuel-injection system is one of the three usual suspects for misfiring. Bad injector spray patterns can be a cause—not because of "making multiple sparks", as has been correctly pointed out (because on a Prius they inject into the manifold, not into the combustion chamber), but just because either the injected volume is changed beyond the roughly ±20% the ECM is able to learn, or, worse, the volume change is worse for some injectors than others (because the ECM can only learn an overall fuel trim, not one for each injector). If the pattern changes from a fine spray to more of a squirt, less of the fuel gets atomized into the mixture and the effect is a lot like burning too lean (except that there's also a bunch of unburned fuel in the exhaust, chowing down on the catalytic converter).

    So, any given car with a misfiring/knocking problem could have an injector issue, but also could have any of the other issues that cause those symptoms. An easy way to nail down whether it is the injectors or not is to send them to a service that cleans and restores them and provides written before/after test results. On PriusChat, that has been going on for Gen 1 and Gen 2 injectors (they use the same part) for several years now.
    You can see examples where the injectors were proven not to be a problem (here, for example), and where the injectors were caught red-handed and shown to be the problem (here, for example).

    So far they've been turning out innocent about twice as often as guilty, but the guilty cases do happen.

    -Chap
     
  18. DJ Q

    DJ Q Junior Member

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    Mine was definitely burning way too lean.
    On cold start you could have smelt it.

    I'm not saying this is the only fix for the issue, but I've had no problems since.
    Went from 18km/l to >24km/l for the tank.
     
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  19. nicolas.bray

    nicolas.bray New Member

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    Just thought I'd share that this seems to have worked for me.

    I had occasional pretty bad knocking (like "is my engine actually damaging itself" level bad, soundwise) at start up. Replaced the spark plugs thinking that would be it but it persisted. Decided that $8 on a bottle of Techron would be worth a shot and it hasn't been a problem since. Pretty sure my fuel efficiency has gone up too.
     
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  20. Krall

    Krall Junior Member

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    Sorry to bump an old thread, but can anyone tell me where I can read up more about the knocking under load? Mine is doing that and I’m not having much search luck, pretty much everything is about the cold start knock.

    Thanks!
     
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