Prius III engine knocking at high torque low RPM (solved)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Kortenbach, Jun 10, 2013.

  1. Kortenbach

    Kortenbach Junior Member

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    I bought my GenIII prius a few months back and, after a while, I noticed that the motor would start shaking in low RPM - high torque conditions. I went to my Toyota garage, but they cound'nt tell me what was wrong, so I did some investigating of my own:
    - All engine mounts seemed OK.
    - New sparkplugs --> still same problem.
    - Connected ODBII plug --> nothing special.

    Then a read a thead about clogged EGR piping that seemed to fit the bill. So I started to take out the intake manifold. Bingo ! The car is running fine now and I decided to put the solution on Prius chat together with some photos that show what is going on.

    EGRDetail.jpg
    Firstly: This is the EGR piping. It runs from the exhaust to the intake on the right-hand side of the engine. It makes the engine more environmently friendly in that it reduces N2 emissions by making the engine run cooler than normal. As a bonus fuel economy increases as well...

    clogging.jpg
    I took of the air intake, airfilter (screws are inside!) and intake manifold, and this is what I found. Yuck!!!

    ClampAndIntake.jpg
    Before you take off the intake manifold open the intake valve (just rotate 90 deg) and check for any excess oil inside. If there is a puddle of oil use some toilet paper to soak it up. Take care when removing the two coolant hoses. I used a clamp to make sure no coolant leaked out before removing the two hoses. All the other hoses connected to the intake manifold just contain air.

    LeftHandIntake.jpg
    So, what happens when the EGR channels inside the intake manifold get clogged ? Well, in my opinion the 'cold' intake manifold makes the carbon and oil vapour in the exhaust gasses 'condense' inside the intake manifold. The clogging advances from left to right (seen from the front of the car). Above picture shows the intake of the leftmost cilinder. It is clean because no exhaust gasses could reach this cilinder because of the clogging.

    RightHandIntake.jpg
    The rightmost cilinder however did get more than it's fair share of exhaust gasses. Normally every cilinder would get an equal amount of exhaust gasses, but now the rightmost cilinder gets all, causing the 'misfire' behaviour.

    Cleaning.jpg
    I took the manifold to the workbench and cleaned all channels with a toothbrush with a piece of rubber tubing attached (don't forget to clean the small holes leading to the engine !). I used "wasbenzine" (Dutch. EN: benzene ?) but I am sure normal gasolene would do the trick a well.

    After I put back the whole thing I noticed a strange "gasket" stuck between two flanges:
    gasket.jpg
    It turned out that someone (I suspect the Toyota dealer !) had put a piece of metal inside to reduce the amount of exhaust gases flowing to the engine (with little success):

    GasketOut.jpg
    Notice the strange shape of the hole. It almost looks like the exhaust gasses punched a hole through the plate !?

    I would love to hear what other people have to say about this. I think that every Prius with reasonably high milage will, sooner or later, suffer from this problem. So please, if you had similar problems put your reaction below. Thanks !
     
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  2. Maroon

    Maroon Member

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    Looks like a homemade EGR blockoff to me. I guess it was an attempt to prevent the manifold from gunking up. Probably worked until it got a hole in it!
     
  3. Bill Norton

    Bill Norton Senior Member

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    Yep, the previous owner thought he was doing some "High Performance Mod" to his Prius.
    What a goof.
    Did you have it long enough to get any fuel mileage numbers before and after fixing his 'mod'?

    Also, could you tell if there was the 'oilyness' on the EGR valve side of that block off plate?
    Usually what comes from the exhaust is dry carbon-like deposits. ( unless the engine is a big time oil burner)
    The Intake Manifold is typically a little oily because of the PCV valve venting oily crankcase air into the intake stream.
    Could it be that without the normal flow of EGR the oily film is building up faster than normal?
     
  4. Kortenbach

    Kortenbach Junior Member

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    I think they did it because the previous owner had similar problems as I did and the dealer decided the card did'nt need EGR anymore. If that's the case I would say i'ts a pretty bad habbit ! Did anyone else find a similar 'workaround' onder the hood of his/her Prius ?
     
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  5. Kortenbach

    Kortenbach Junior Member

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    Bill: I think it may bee too early to tell since I finished the yob only yesterday, but I got a 2,5l/km readout on my 5min MPG indicator today (about half of the average milage). As far as I know that never happened before ! I'll try to give you an update on fuel consumpion the coming weeks...
     
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  6. Bill Norton

    Bill Norton Senior Member

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    Dang, you think a dealer did that???? A Real Toyota Dealer?
    What kind of back yard dealer would do that? If so, I'd try to report them...
     
  7. Kortenbach

    Kortenbach Junior Member

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    Well... the car has always been serviced by a Toyota dealer... Can't be sure though...
    Since this problem should occur in any Toyota Pruis with High milage (?) I am curious to see what other people had done to their Prius to prevent or solve this clogging problem.
     
  8. Maroon

    Maroon Member

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    Maybe they thought they were blocking off the PCV flow. But yeah, a gunked up intake mani on a high mile Prius isn't a surprise. However, I would think your fuel consumption would decrease since the exhaust gases also help the engine warm up faster on a cold startup.
     
  9. Kortenbach

    Kortenbach Junior Member

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    Bill: "Also, could you tell if there was the 'oilyness' on the EGR valve side of that block off plate?"
    The block-off plate was not oily on either side. The oilyness started just at the end of the stainless steel EGR tube leading to the intake manifold. I think that some sort of "condensation" of smoke-particles is taking place in the intake manifold (?).

    B.t.w. I found several web sites that sell these "EGR block off plates". It seems to be a common "solution" to EGR problems...
     
  10. The Critic

    The Critic Resident Critic

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    Thanks for posting this, I may check mine at some point in the near future. How many miles do you have?


    iPhone ?
     
  11. El Dobro

    El Dobro A Member

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    I wonder if the previous owner also owned a TDI. :D
     
  12. Den49

    Den49 Member

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    Back in the 80's and 90's, before onboard computers and when EGR was less accurately controlled, if there was too much EGR flow the engine would stall at slow or just above idle speed. The solution was to install a filter or plate to partially block the EGR passage. I did this on a 5.0L 1990 Crown Vic because there was no other economically feasible solution at that time. Perhaps the Prius in this case was also experiencing the same type of EGR stalling and instead of fixing it, which should be a lot more feasible now than in 1990, the owner chose to install the plate you found. Looks like an old school solution used to avoid a high cost repair on an old car.

    Thanks for the excellent post.
     
  13. Former Member 68813

    Former Member 68813 Senior Member

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    Interesting, this is the 2nd time I'm hearing this issue. This was the first time: P0304 MISFIRE ON CYLINDER 4 | PriusChat

    Incidentally, both those affected prius cars were European ones. Coincidence?
     
  14. spiderman

    spiderman wretched

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    Kortenbach, what country do you live?
     
  15. Kortenbach

    Kortenbach Junior Member

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    I live in the Netherlands.
    I did about 200km now with the EGR fix.
    It looks like the car uses about .2 liters per 100km less than before.
    I asked a collegue of mine if I could have a look under the hood of his 2010 Prius. I could find no evidence of a blockoff plate in his car. His car did about 140,000km.
    I am stil puzzled by this. I hope to hear some more about people's experience with high milage gen 3 Priuses and their EGR's.

    In the mean while I read the thread about P0304 misfire. Somewhere in the end someone suggested worn piston rings as the underlying problem. Doe anyone have an idea how to check for this ?
     
  16. spiderman

    spiderman wretched

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    You can do a compression-check, but unless you had serious problems there, I don't think you would get the misfire.
     
  17. Kortenbach

    Kortenbach Junior Member

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    It's not the misfires I was wondering about. It's the oil puddle in the intake manifold and the clogging of the EGR channels. I think they may be caused by faulty piston rings...
     
  18. Former Member 68813

    Former Member 68813 Senior Member

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    That comment was directed at a poster who highjacked that thread. You have to read the whole thing.

    As far as I can determine from reading priuschat, oil in intake manifold is a common finding. I also saw it in my corolla when I replaced manifold gasket. Oil gets there via PCV. Not sure what is the source of EGR deposits. If you had problems with piston rings, it would show as oil consumption (oil control rings problems) or low compression (top rings problems).
     
  19. Kortenbach

    Kortenbach Junior Member

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    Ok, my idea was that somehow excessive amounts of oil get into the exhaust gasses and cause the EGR clogging. The only way they can get there is excessive pcv blowby or worn piston rings (oil scraping rings)... Or am I mistaking ?
     
  20. edwardob

    edwardob Member

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