Death Rattle... clean manifold & EGR, new plugs, no change

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Nor'easter, Oct 13, 2021.

  1. Nor'easter

    Nor'easter Member

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    I did. Everything in the EGR system looked fine, dirty, but open and functional.
     
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  2. Mendel Leisk

    Mendel Leisk Sand Pounder

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    No warning lights? No misfire codes, P03XX?

    It "sounds" like head gasket failure; try a leak-down test?
     
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  3. Nor'easter

    Nor'easter Member

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    You have a point about the Prius Chat echo chamber for sure. My task yesterday was to get all the maintenance caught up, which I did. It was pretty clear once I was in there that I'd discovered no smoking gun, so I expected the problem to remain.

    Now in my case, the car runs fine at idle and wide open, it runs like crap at low load... pretty much anywhere on the right side of the HSI display up to where the "power" indication begins. If it's in the "power" range up to wide open, it runs fine.

    It's never been terribly clear to me how the Prius engine manages valve timing (atkinson cycle) and egr as a function of load and engine speed (and maybe other things). I'd like to understand that.
     
  4. JC91006

    JC91006 Senior Member

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    It would be surprising if this does end up to be a bad head gasket. As this car seems to be cared for with minimal oil burning, EGR seemed clean.

    But there's also the water pump, if that failed or working intermittently, car can get hot and result in a head gasket failure. My mechanic bought a 300k miles car that had similar symptoms, rattling at low rpm, drives fine at high speed/rpm. Ended up being a bad head gasket.
     
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  5. Nor'easter

    Nor'easter Member

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    No codes, pending codes, warning lights. Coolant level steady, no white smoke. Fuel economy is good, oil consumption nil.
     
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  6. Nor'easter

    Nor'easter Member

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    I'd be sad if a WP failed at only 120K on this car! It's interesting you cite a case of a car with blown HG that ran well at high speed, duly noted.

    Next step for me is to get techstream running again and see if I can suss out something that looks like an air leak or similar that's upsetting mixture at low - med load but not at idle or high load. In my experience smooth running at high power rules out ignition problems (but I'm not a pro).
     
  7. JC91006

    JC91006 Senior Member

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    I changed out my water pump at 135k miles on my 2010. As a preventive measure since it's over 10 years old.

    I suspect if you did have a head gasket failure, it's at a very early stage. But not having any misfire codes and rattling like that, is very puzzling.
     
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  8. jzchen

    jzchen Senior Member

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    Things, ie EGR, may get stuck closed, they may get stuck open, or maybe even somewhere in between. I would venture yours may be stuck open, hence the suggestion to close it and see if the problem disappears.

    REVVL V+ 5G ?
     
  9. ChapmanF

    ChapmanF Senior Member

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    If the valve sticks open, the engine's normal idle is likely to be poor.

    If you have Techstream, you can use the active tests to send the valve to different step positions and note the effect on idle quality and manifold pressure. This is an easy way to confirm the valve moves without breaking out the wrenches.
     
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  10. Nor'easter

    Nor'easter Member

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    Just had a look at the embedded video. Very nice! If I can get out of this for a $180 EGR valve kit I'll score as a win.

    Has anyone followed up on the ECU update end of things? DIY with techstream?
     
  11. Mendel Leisk

    Mendel Leisk Sand Pounder

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    EGR diagnostics from Repair Manual attached:
     

    Attached Files:

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  12. JC91006

    JC91006 Senior Member

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    There was a TSB from Toyota that addressed the EGR valve, it has an extended coverage for 10 years. Your car is slightly over that time frame for it to be covered by Toyota.

    If I recall correctly, the language on that TSB suggests this would be a problem on cold starts, where the engine would rattle. And there would be a code that's thrown. I think your experience is not just on cold starts, it happened when it's nicely warmed up.
     
  13. jzchen

    jzchen Senior Member

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    I did the flash DIY. But left old EGR and intake manifold. Requires a more expensive VCI, (mine's from Drew Technologies), and the $65 subscription level. Not too hard, just getting the setup right (to connect to their server properly) wasn't intuitive...

    REVVL V+ 5G ?
     
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  14. jzchen

    jzchen Senior Member

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    @JC91006 I updated my post #19 with the first two pages of each for reference which models are covered, warranty details, and part #s, as of last fall...

    REVVL V+ 5G ?
     
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  15. burebista

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    Or if you don't have Techstream but you have an OBD reader you can do an empirical test like me.
    As you can see, idle, EGR valve closed MAP sensor shows some vacuum and MAF sensor almost nothing.
    On the road, EGR valve open and MAP sensor close to atmospheric pressure and MAF sensor shows some airflow.
    So it seems that EGR valve is working fine.
    Or at least I hope so.:D
     
  16. ChapmanF

    ChapmanF Senior Member

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    Can't forget, though, that "on the road" there are other reasons for the MAP to be close to atmospheric and for the MAF sensor to show some airflow. Like, the throttle being open, because you're on the road.

    That's why it is hard to tease out any EGR effect from MAP and MAF values while driving. (The ECM's own EGR monitor routine does that, but does it at very specific times while driving, and does it a very specific way.)

    A MAF reading doesn't reflect EGR flow anyway; it enters downstream of the sensor.
     
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  17. burebista

    burebista Member

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    I know, that's why I said an empirical test. :)
    I'll try next time to do another test on the road. Keep a steady acceleration with EGR valve open and maybe at some point it will close itself and then I'll watch changing in MAF/MAP sensors.
    But I must work with my wife for that because she's the driver. :whistle:
     
  18. ChapmanF

    ChapmanF Senior Member

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    The difference between whether a test is workable or not isn't exactly the same as whether it's empirical or not.

    Most of the useful stuff learned over the ages has been thanks to workable empirical tests.
     
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  19. Nor'easter

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    Update:

    I got Techstream running on a new/old laptop.

    At idle (maintenance mode), I hear something that sounds like a (pulsing) vacuum leak in the vicinity of the EGR. I squirted some brake cleaner at flanged joints on EGR valve inlet/outlet, no change noted. Fuel trims are good (few percent, rarely +/- 5).

    I ran the EGR valve active test in maintenance mode. EGR valve seems to work normally (smooth when closed, roughness begins at around 10, increasing roughness with increasing opening).

    I blocked the EGR at the pipe inlet with a shim cut from a beer can. Verified that EGR was blocked completely in active test.

    No change in symptoms described previously. Engine runs fine at idle and high power, very rough in low/mid range. No misfires. Fuel trims in normal range.

    I pulled the shim out, then introduced a small intentional air leak at the same place with a knife blade. This may have made symptoms slightly worse (fuel trims stayed in normal range, less than 5%, no obvious change here). The rubberized gasket between EGR valve and pipe didn't look great when I had things apart, it might be leaking a very little bit. I'm considering applying a little high temp rtv to this to see if this helps (don't have a new gasket handy).

    At this point, I think I've ruled out a leaking EGR valve. If the EGR pipe gasket is leaking, it isn't much -- I don't think that's the problem I'm looking for.

    Other things to look at?
     
  20. Nor'easter

    Nor'easter Member

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    Added a little RTV to the EGR pipe/EGR valve gasket. No change.

    Engine runs very rough when in park with electrical loads on & engine starts to charge the traction battery. No codes, no misfire indications, no obvious clues in live data.
     
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