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2nd gen start knock but no codes for misfire

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by ozmatt, Jan 31, 2021.

  1. ozmatt

    ozmatt Active Member

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    Hi all

    I have a rather poorly maintained 2008 with 530,000km poor thing is really rundown! has filthy water for coolant containing nasty sandy like stuff which i presume is either old radiator stop leak goope that has failed (used to have a crack in the expansion tank) or broken down plastic floaties from the failed expansion tank, it had utterly filthy oil and inside the rocker cover is extremely dirty, top end and lifters are constantly noisy (more than usual) ..

    have changed the oil and purge the filthy radiator with fresh water most days in hope the sandy stuff clears away, eventually! wont bother adding coolant until its clean-ish.

    Been wondering seeing there is no misfire related engine codes (any codes for that matter) could this potentially be a mechanical problem like valves, lifters, chain in transmission? so my question is what other than fuel injector or coolant leak down might causing the cold start rattles


    cheers all thanks for reading :)
     
    #1 ozmatt, Jan 31, 2021
    Last edited: Jan 31, 2021
  2. Aaron Vitolins

    Aaron Vitolins Senior Member

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    You could have a very small headgasket leak that lets a very small amount of coolant/or (sandy water?!) into a cylinder causing a rough start.
     
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  3. edthefox5

    edthefox5 Senior Member

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    Blown motor.

    go on you tube look up

    Prius inspection

    it will show you how to put the motor in inspection mode where it will continuously idle till you shut it off.
    While running get under the car and listen to the bottom end.
     
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  4. mr_guy_mann

    mr_guy_mann Senior Member

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    At that many km with poor maintenance anything and everything is suspect. It could be a mechanical noise until oil pressure builds up such as timing chain slack or worn rod bearings. It could be anything marginal that IS causing a misfire, but not long enough or bad enough to set a code. If it's that poor of a condition, how much effort you want to put into it? I would do minimum basic repairs and drive until something gets worse (or dies).

    Posted via the PriusChat mobile app.
     
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  5. ozmatt

    ozmatt Active Member

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    Hi Aaron, yeah maybe but i inspected the plugs a couple times they always look clean, and correct me if I'm wrong but if that was the case I would expect to see misfire codes

    Hi Ed, it's got a noisy top end but I'm pretty sure there's no noise from the bottom end in inspection mode or under driving load, could be wrong but that's not what it sounds like to me!
     
  6. ozmatt

    ozmatt Active Member

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    I thought tech stream would report and count all misfires? with coolant leak down or bad plugs etc (btw plugs are new)

    Timing chain is a good explanation, it sounds a bit like that I can't really feel much of a "shake" like misfire, it's more like just noise as in mechanical clutter/ rattle.. are chains known to cause this?

    I only want to put in enough effort to nurse it through if it's NOT coolant leak down, if it IS leak down I will put an engine in it when it fails

    Thing is, it goes quite well so if it's infact not leak down this old thing could chug along for ages longer yet, 1nz is reasonably resilient, I'm just looking for explanations really :)
     
    #6 ozmatt, Jan 31, 2021
    Last edited: Jan 31, 2021
  7. ChapmanF

    ChapmanF Senior Member

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    When my 2001 1NZ developed its occasional cold-start knock, it remained a mystery for the remaining years I had the car. Compression was fine and there was no loss or mixing of coolants, I had a few different experienced mechanics listen and say they were sure it wasn't anything bottom end, valve adjustment seemed sort of tolerable if not perfect everywhere, the #4 cam lobes looked a little bit like maybe less oil reached them, but nothing definitive there. There just never turned out to be any smoking gun, and in my case it never led to any more serious problem. It just remained a puzzle.
     
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  8. ozmatt

    ozmatt Active Member

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    hope im this lucky! it only needs to last a little while but the longer the better

    how occasional was your issue happening, for me its nearly every day but it seems to skip some days which really throws me off, pretty sure its more severe if the car is used a lot the night before
     
  9. ChapmanF

    ChapmanF Senior Member

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    Not sure I remember exactly. Seemed more frequent in cold weather. Often enough it bothered me, but also unpredictable enough that I had several instances of not being able to make it happen for some mechanic I wanted to listen to it.
     
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  10. ozmatt

    ozmatt Active Member

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    Thanks chapmanF gives me some hope that it might last a bit longer
     
  11. ozmatt

    ozmatt Active Member

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    tossing up what to use to flush out this filthy disgrace of a cooling system

    some say use vinegar, others say C.L.R .. these should be okay if i get it out and neutralize it asap

    apparently off the shelf type alkaline based flushes work better for rust than they do gunk and corrosion

    what you all think about this one
     
  12. drone13

    drone13 Active Member

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    The symptoms you describe are consistent with the VVT Oil Control Valve where it makes a knocking noise of short duration when the car is started, but then goes away. This happens frequently in Toyota vehicles (many different models) that have not had regular oil changes and the valve gets gummed up. Eventually the solenoid dies from being overworked and a code gets thrown because the valve timing can't be changed at all, but if the noise occurs just at start up and goes away quickly you won't see a code. If as you said, the noise is coming from the rocker area it's worth looking at since it's easy to check and it's only a $20 part to change out. If the solenoid is still working well then just pulling and cleaning the valve could fix it.
     
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  13. ozmatt

    ozmatt Active Member

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    thankyou Drone13 this is more hope the engine could last a little longer.. i will do some research on the vvt oil control valve and give it a good flush and a couple changes over the next few thousand Ks,

    another thing maybe worth mentioning is, i have 10w40 dino in it currently to as i plan on doing a couple short oil change intervals to flush it out which is what the previous owner used anyway

    next oil change i will try w30 see if that changes anything
     
  14. ChapmanF

    ChapmanF Senior Member

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    Can you point me to more on this? It's an explanation I hadn't seen before and seems worth knowing about.

    Are you saying the solenoid valve gets gummed up, or the vane actuator on the camshaft? Or both?

    What produces the knocking noise?

    What are you calling the $20 part to change out? The solenoid? (I've assumed the vane actuator is more than that.)
     
  15. mr_guy_mann

    mr_guy_mann Senior Member

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    Right, it is usually the VVT actuator (cam sprocket) that has the problem. Specifically there is a pin that locks the VVT in "park" position when oil pressure drops. Wear or deposits cause the pin to not seat or lock. So on startup valve spring pressure pushes on the cam lobes as the cam turns, causing the guts of the actuator to jump forward and backward against the internal stops until the system builds up oil pressure.

    Don't see this problem very often on Toyotas.

    Posted via the PriusChat mobile app.
     
    #15 mr_guy_mann, Jan 31, 2021
    Last edited: Jan 31, 2021
  16. ChapmanF

    ChapmanF Senior Member

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    Interesting! I knew about that pin (or at least inferred there must be something like it, from the compressed-air trick shown in the repair manual for rotating the actuator). This is the first I've heard this problem mentioned.

    Is it something you've run into more often in other makes? Have you run into it on some Toyotas? Do you know of any articles, service bulletins, youtube vids, etc., that would have any more details about it?
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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    I have seen a couple of times on older Honda 2.4L Accord and CRV- there's a TSB for it (# 09010) - you replace the VVT actuator (and I do the timing chain if it's worn enough). I also had a confirmed fault on a mid 2000s Camry 2.4, but that car was too overall tired to justify the repair cost.

    It can be difficult to differentiate a VVT rattle from a timing chain rattle unless you pull the valve cover to verify if the VVT is locked or you have chain slop.

    Posted via the PriusChat mobile app.
     
  18. edthefox5

    edthefox5 Senior Member

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    G2 has a VVT oil filter right next to the solenoid to prevent this exact occurrence. Not sure if the G3 has a filter.
    It will be a hex head bolt head.

    I recently replaced my solenoid with a Red Bullet works really good.
    Motor really likes the advanced timing and no pinging. Very peppy.
     
  19. drone13

    drone13 Active Member

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    I'm not say it's the problem, but there's lots of history with Toyota cars with this issue. The issue exists on Scions, Camry, Corolla, Prius and others. Not a really frequent occurrence, but common enough for the symptoms you mentioned to be worth looking at.

    My understanding is that the valve refuses to move from being gunked up and that leaves the valve timing at the last position it was at before shutdown and the solenoid can not produce enough force to move the valve in to the proper position until either the oil pressure increases from the pump or the oil heats up and the pump becomes more efficient. So the force needed to move the valve increases for a short time and the solenoid can't deliver enough force. This is heard as a knock from improper detonation in the cylinder, usually pre-ignition because the timing is now sub-optimal for a start. Once the oil pressure builds from a start there is enough pressure to at least come close to the demanded timing change by the ECU and everything is groovy again. But it might still be off, just not enough to throw a code. If it can't achieve proper timing changes you will see reduction in fuel economy even without a code, and as the problem gets worse it can be a significant fuel economy change. That would be another indicator of this issue, but might not be as easy to notice.

    I suspect there is a delay in the engine start sequence where the ECU ignores the timing change values for a short time period, but if it continues a code will be thrown. I have no way to verify the algorithms used by Toyota and I don't think they published them, but after working on emission system programming for another auto manufacturer for many years, I suspect that to be the case.

    BTW, this can also occur from a failing solenoid.

    Take my opinion with a grain of salt, but the symptoms you mentioned at least warrant a quick check.
     
  20. drone13

    drone13 Active Member

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    The entire part, valve plus solenoid is a single assembly you buy. It available on Amazon, even as a Prime item for under $20. I haven't check Toyota, so I would guess 5x that price...lol.