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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    Checking coolant for exhaust is a good idea. I have not done this, but there is absolutely no sign of
    white smoke
    coolant loss
    coolant in oil
    oil in coolant
    (edit) or any sort of froth in the coolant

    Also, engine purrs like a kitten in maintenance mode (no load idle) and runs great at high load.

    Trans fluid was changed at 100k miles, probably not before (I bought at 98K). Genuine Toyota W/S as called for by owner's manual.
     
    #61 Nor'easter, Oct 18, 2021
    Last edited: Oct 18, 2021
  2. Nor'easter

    Nor'easter Member

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    I understand the mechanical design of the transmission.

    I agree that the "chugging" is roughly speaking engine rotation frequency. I get that this sounds like a head gasket -- because a blown HG is one way to get a big torsional excitation going, which is what we see here. But for reasons already stated, I don't think a blown HG is what is causing -my- big torsional excitation.

    Now this is a walk on the wild side, but... I think there's a way to do a fuel cut in TS one cylinder at a time. Not sure if you can do in ready mode or just maintenance mode. If it can be done in ready mode, then would this be a <safe> way to confirm or refute misfiring? Obviously, if I fuel cut #1 and nothing changes, that would be a pretty solid clue that #1 is misfiring. And vice versa.

    back to MG1... is there a way to see what the hybrid system is commanding for torque on MG1, and would it show me an instability (at e.g. 16 - 20 cycles per sec) if it existed? Various comments have been made over the years (and earlier in this thread) about the need for the hybrid system to synch nicely with the ICE... but I don't know how to dig into this further.
     
  3. ChapmanF

    ChapmanF Senior Member

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    As the AECS article pointed out, there's a limit to how much you can learn from individual injector cutoff in a Prius, because the Atkinsonoid intake valve timing means some fuel-containing intake charge is always being pushed back into the manifold from adjacent cylinders.

    You can read back MG1 torque and RPM in the real-time data list. What you're likely to find is that they come back as numbers in CAN bus packets, on a schedule that is too coarse, with too much latency, and too unrelated to the rotational period, to be of much use for the kinds of questions you're wanting to ask. You might be better off tapping your own instrumentation into the phase current sensors and resolver.

    I'm not positive it would be worth the effort. Because MG1's RPM is most often so different from the engine's, and not even different by something like a tidy integer multiple, I think Occam's beard would grow very long and shaggy before you'd find the cause of an engine-synchronized rattle to be originating with control of MG1.
     
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  4. Nor'easter

    Nor'easter Member

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    Thanks.... that was a great reply. So you are still going with "misfire".

    Alright. What is a/the misfire scenario might I be looking for? Again -- runs perfect in maintenance mode (no load) and at full throttle.
     
  5. ChapmanF

    ChapmanF Senior Member

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    It does seem like a bit of a head-scratcher. That Toyota Tech article linked back in #49 does devote a bit of ink to ways of focusing your diagnosis on the load range where the problem is most apparent, as you don't get much useful information in the light-load or full-throttle ranges where it isn't showing up.

    It kind of seems as if you're getting variations in crank acceleration large enough to make rattles but maybe not quite large enough to bump misfire counts. That complicates matters, as then you don't get the handy freeze frame data you would get when the ECM actually counts a misfire. But you can maybe still employ a lot of the same ideas. The article did say "when duplicating the misfire conditions, misfire margin usually reacts before the other data list values are displayed." It appears you did see the margin go negative at least once back in #57, along with flashing yellow, though I wasn't sure under just what conditions or for how long. The margin may be the most sensitive indicator you've got going for you in this kind of borderline situation; if you can find a way to reliably create the conditions where the margin goes lowest, then you can start gathering whatever data you can under those conditions. Maybe a scope on ignition coil output, using the wrapped-wire trick from AECS. Supposedly the shape of each spark discharge trace can tell you more things about mixture, compression, and combustion than just basic sparked-or-didn't-spark. At least if you have Obi-Wan around to look at the traces. (I am not Obi-Wan,)
     
  6. jzchen

    jzchen Senior Member

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    Already covered? If so my apologies.

    What's the oil level on the dipstick? What oil: brand, model, weight is in there? I want to check the Ca/Mg levels specifically.

    REVVL V+ 5G ?
     
  7. Nor'easter

    Nor'easter Member

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    This car has been on synthetic since new. In it now is 5w-30 Pennzoil Platinum, last changed about 1500 miles ago. Previous oil changes I've done were 0w-20, either Pennzoil Platinum or Mobil 1 AFE, I'd have to check. Change to 5w-30 was mostly for convenience (I use in other vehicles). I fill to the full mark on the dip stick and oil consumption is nil. There was -maybe- 5ml of oil in the bottom of the IM when I cleaned things out. PCV valve only a little dirty, still rattled, I changed anyway when things were apart, replaced with Toyota OEM.

    I sent an email with link to video to a toyota "specialist" here in NH. I hope they reply, I need some new eyes, brain cells and probably equipment on this job.
     
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  8. jzchen

    jzchen Senior Member

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  9. Nor'easter

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  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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  11. Nor'easter

    Nor'easter Member

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    Thinking about this for a minute, I'd bet a lot of money (about the cost of a head gasket job, for instance) that what I'm seeing isn't LSPI. It's too regular. And there isn't a hint of the high frequency ringing that is the telltale for end gas detonation (what everyone outside the Prius community calls "knocking") which I'm about 90% certain would be an inevitable result of LSPI.
     
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  12. Nor'easter

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    In Techstream, there is a Knock Correction Learn Value, that in my case is 21 degrees. Is this typical? That's a mighty big number....

    (edit) TSM says normal is 0 - 22 deg.
     
  13. Nor'easter

    Nor'easter Member

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    Dropped car off with local Obi-Wan. On way over, ears and butt dyno say it's misfiring at low/mid power, but still fine at idle and high power.
     
  14. Nor'easter

    Nor'easter Member

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    Obi-Wan took a look, says it's the transmission damper that's making the most horrible noise from the transaxle area (I agree). In his opinion, the engine is running fine, "it is not misfiring at all". Hmmmmm. So he agrees with the ECU (no codes). That's where I started out, but at this point I'm much less certain. Something is setting this cascade of torsional oscillations off (and keeping it going). When driving the car at low/mod throttle, HSI indicator on the right side but not into the "pwr" region, there is a sensation of power loss at times.

    Sheesh. Okay, well I can yank the plugs, do a leak down test, endoscope the cylinders, that's all pretty easy, but the expected result is "no problems".
     
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  15. jzchen

    jzchen Senior Member

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    Knock sensor is listening. Sounds like knock, retard timing, loss of power...

    REVVL V+ 5G ?
     
  16. Nor'easter

    Nor'easter Member

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    Interesting point, thanks. Knock sensor is listening for ringing after detonation, about 6KHz iirc. The ringing is a resonance in the high pressure gas inside the cylinder, not the ringing of metal parts. So, I need a bang sensor in addition to knock sensor :). I actually have chassis ears, but in this case I don't really need them.

    (edit) There is one knock control event in a log I recorded. That's interesting... but I don't think it's the main story. I'm going to go for a ride and log some more.
     
    #76 Nor'easter, Oct 22, 2021
    Last edited: Oct 22, 2021
  17. Nor'easter

    Nor'easter Member

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    Did all my errands today with the Prius... 50 miles, 61+ mpg recorded for the trip on the dash display. Don't see how that happens with an ICE that is wounded and misfiring. Rattles disappear instantly if you floor it.

    Obi-Wan clearly not salivating for this job (I don't blame him, lol, Prius isn't really his thing).

    Meanwhile, another shop I engaged via email has replied and also thinks (based on that video and other detail I provided) that the damper is the main problem.

    I presume the repair begins with step 1) remove engine and transaxle. Can anyone hazard a guess at the time / labor here?
     
  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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  19. ChapmanF

    ChapmanF Senior Member

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    Certainly a casualty of misfiring, whether that is caused by coolant in the combustion chamber or by any of the other things that cause misfiring.
     
  20. Nor'easter

    Nor'easter Member

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    You'd think that enough misfiring to fail a damper would have thrown a DTC (?).

    As previously mentioned, I'll have a look inside the cylinders and some compression & leak down results, plus some professional eyeballs on the job before we commit to serious repairs.
     
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