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Prius Gen 3 strange noise during slow acceleration

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by GabrielD, Apr 29, 2021.

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  1. ChapmanF

    ChapmanF Senior Member

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    :eek: For anybody else considering this test, please review this post that recaps some of the ground rules for the test from the Repair Manual (more info). Among them: keeping the test duration to ten seconds or less, and no going above step 30.

    Getting anywhere near step 30 in that test before shaking sets in suggests that EGR investigation is in order.
     
    #21 ChapmanF, Apr 30, 2021
  2. GabrielD

    GabrielD Member

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    I managed only to clean sensors (MAP, MAF) and throttle body. EGR valve and pipes, and intake manifold where cleaned October 2019 (details here)
    I also disassemble EGR valve and tried to find a logical way to put it back (magnet slowly revolutes back after fully screw it).
    Important thing I noticed was that ICE starts very rarely and consumption is improved for sure, I will check that next days.
    The noise almost is gone, not totally I can still hear it, much more faded, at 35-40 slow acceleration, ICE running). On electric, no sound, therefore no bearing problem...
    I took Techstream data and try to compare to see improvements...
    I noticed some misfire count, could be this the issue?
    In this 2 pictrures attached, before and after cleaning I can observe misfire, but also atmospheric pressure, I think always shows 93 kPa, and in my area presure is 1010 kPa.
    Can someone confirm this sensor shows another value? I always see it at 93.
     

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    #22 GabrielD, Apr 30, 2021
  3. ChapmanF

    ChapmanF Senior Member

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    The way the rotor spins back out a little is actually doing you a favor.

    It means that once you have the stator replaced and the screws tightened down, the valve will be slightly open.

    That gives you a chance to push it gently closed with your thumb and confirm that it moves smoothly without binding.

    You wouldn't get the chance to confirm that, if the rotor stayed put and the valve ended up already closed when reassembled.
     
    #23 ChapmanF, Apr 30, 2021
  4. GabrielD

    GabrielD Member

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    Good to know that, thank you. Any reason to try another position for EGR, or somehow the system finds itself the proper position? Now, i am thinking that my problems come from cylinder 4, I think after misfire, all the other (engine rpm, MAP, injection volume, EGR position) are dropping down...
     

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    #24 GabrielD, Apr 30, 2021
    Last edited: Apr 30, 2021
  5. ChapmanF

    ChapmanF Senior Member

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    From the repair manual, the system seems to have about the simplest possible strategy for finding the proper position: whenever the engine is idling, the ECM just never stops driving the motor in the "close the valve" direction.

    [​IMG]

    So pretty much wherever the valve was before, it ends up finding where 'closed' is within a couple seconds, any time unless the valve is truly stuck open and can't move.

    Then under non-idle conditions where the ECM wants, say, n steps of EGR, it just counts up n steps from there,
     
    #25 ChapmanF, Apr 30, 2021
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  6. GabrielD

    GabrielD Member

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    After a 20 min drive, the problem still appears. So, cleaning sensors was good for my car, but not enough.
    Still misfire on cylinder 4. I changed all the plugs, and keep coils to their positions, same cylinder 4 error.
    I changed coil nr. 4 with coil nr. 2, still cylinder 4 misfire.
    What else should I try? Could be injector cause of misfire?

    later edit:
    It seems one of our coleagues, Catalinux, had same problem, but in his case with P0304 DTC error.
    He changed injectors, sparks and coils, crankshaft and camshaft sensors, even transaxle he tried, and finally discovered that problem to be on intake manifold obturated channels... (post nr. 17 here).
    I will go for it too...
     
    #26 GabrielD, May 1, 2021
    Last edited: May 1, 2021
  7. GabrielD

    GabrielD Member

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    After EGR cleaning, I am proud to report that all the problems I had, are gone.
    No misfire, improved driveability, at 170 km/h engine is bearly heard...
    Here are some pictures, notice that I am doing cleaning EGR and cooler after 20.000 km
    I also notice a crack in rubber engine support...
    DTC right after cleaning, P0102 (MAF Sensor – Circuit Low) and P0113 (Intake Air Temperature Circuit High Input)
     

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    #27 GabrielD, May 6, 2021
    sLick415, Raytheeagle, ASRDogman and 1 other person like this.
  8. Grit

    Grit Senior Member

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    great work, lookin good. In your option, do you think a stuffed up EGR circuit would lead to head gasket failure?
     
    #28 Grit, May 6, 2021
  9. GabrielD

    GabrielD Member

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    It's hard for me to say that, but it's obvious that a EGR cleaning prevents head gasket failure and get rid of misfire and shaking...
    I am thinking that EGR is not so good for engine... taking hot air from exhaust and bringing inside intake...
    I am surprised that last cleaning lasted only 20.000 km, I admit that the cleaning was made by hand using carb cleaner, a steel wire and air...
    This time I used pressure car wash, sodium hydroxide, and results are better.
    Here are some pictures from first EGR cleaning...
     

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    #29 GabrielD, May 6, 2021
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  10. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Yeah sodium hydroxide (lye) solution, and/or pressure washer, is more effective for cooler.
     
    #30 Mendel Leisk, May 6, 2021
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  11. GabrielD

    GabrielD Member

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    One more detail I would like to discuss...
    During my research about EGR function, I noticed this statement(see picture), almost in all vehicles...

    I want someone to explain me how is possible to decrease temperature, when the air you put inside engine is over 2500 F?
     

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    #31 GabrielD, May 7, 2021
  12. Raytheeagle

    Raytheeagle Senior Member

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    Or ;).

    No need to be caustic:LOL::ROFLMAO::LOL::ROFLMAO:.
     
    #32 Raytheeagle, May 7, 2021
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  13. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    I believe it’s cooling the combustion chamber due to being relatively non combustible; it partially quenches the explosion.
     
    #33 Mendel Leisk, May 7, 2021
  14. GabrielD

    GabrielD Member

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    I believe an explosion take place everywhere, even in water or in the deepest freeze place...
    A hot and inerted gas inserted in that chamber only does bad things to the performance (in my opinion).
    Everyone knows the fuel ratio importance, if you mix that with something inerted it's worse than using medicinal alcohol as fuel...
     
    #34 GabrielD, May 7, 2021
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  15. GabrielD

    GabrielD Member

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    In my situation, it was needed the caustic soda....
     
    #35 GabrielD, May 7, 2021
  16. ASRDogman

    ASRDogman Senior Member

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    Apparently, it works. Because they've been sucking exhaust fumes into the cylinders for a long time.
    It's not straight exhaust, it's a small amount. And it's going through the intake, with cooler air.
     
    #36 ASRDogman, May 7, 2021
  17. AW82

    AW82 Member

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    Sorry to sound harsh, but it's better to gain some knowledge than have an opinion. From the Wikipedia page on Exhaust Gas Recirculation:
    Note that it's not saying EGR reduces temperature across the board, but that it reduces peak temperatures during combustion. That is why an uneven distribution of recirculated exhaust gas across cylinders, such as by result of an unevenly clogged intake manifold where the ECU can't sense the unevenness and therefore doesn't/can't adjust timing and fuel trim to individual cylinders and detonation can occur.
     
    #37 AW82, May 7, 2021
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  18. GabrielD

    GabrielD Member

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    Sorry if I am wrong, I just read about it, and other colleagues here say the same: (see pic attached) "..., lowering temperatures in the combustion chamber by almost 150°C..."
    About Wikipedia, I wouldn't take it as a basic source of info...
    Check the second picture, it says now " is lowering temperature with 150 C"...
    here is the link from Wikipedia...
     

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    #38 GabrielD, May 7, 2021
  19. AW82

    AW82 Member

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    Well, earlier in this thread you asked for an explanation of how it is possible for EGR to reduce temperatures. I posted a direct quote from Wikipedia as an answer. Is Wikipedia the best source? Maybe not, but it's an easy place for people to start their learning on a subject and can be found with a simple Google search on a topic. You had stated an opinion that illustrated a lack of understanding about EGR systems, therefore I presented a very easy to find source.

    What is interesting to me is that that line about decreasing in cylinder temperatures was not in the Wikipedia page before about a half an hour ago. It appears that you edited the Wikipedia page about a half hour ago to add that line about reducing temps by 150C. I'm not sure what your point was in doing that, but it certainly looks suspicious. Either way, that reduction noted in both the source you provided and the Wikipedia page you edited is referring to in cylinder temperature reduction. My whole point and stating that it is not across the board temperature reduction is that many people seem to believe that EGR systems reduce overall engine operating temperature by some significant margin. In-cylinder temperatures are substantially higher than for example coolant temperature or other measure of operating temperature.
     
    #39 AW82, May 7, 2021
  20. GabrielD

    GabrielD Member

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    Exactly! Glad to notice that...
    As I did, everybody can edit Wikipedia, that means is not a reliable source...
    Instead of "looking suspicios" you can be more unstressed and look at it as a joke...

    On the subject: do you have an opinion about reducing temperature from my second pic?
    source is here, and I assure you was not edited by me...
     
    #40 GabrielD, May 7, 2021
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