Violent engine shakes at low temps

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by MAW31, Mar 14, 2017.

  1. MAW31

    MAW31 New Member

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    2005 Prius 163,000mi.
    Owned car for 3 years in Florida, just drove it 1200 miles north to Massachusetts.
    In all the time I've owned my car it's ran perfect and the drive up was no different. Good mpg, 22 hrs of shared driving.

    However, the morning after arriving (March 7th) on engine startup, the engine violently shook at idle and continues to run that way. Several days now. The only thing different between the time I parked it and the morning is that it's under 32 here now. Motor is throwing multiple misfire codes and the code for the coolant flow control valve were thrown. I replaced the pump with am OEM dealer provided pump and while I wanted the engine shake to go away, it did not. Back to Autozone for battery test, (it's a new optima) it tested good. Oil level is spot on at the full mark.

    Observed: most of the violent motor shake is at or just off idle AND it WILL go away. While parked and idling with motor shaking and clunking for minutes, it then may totally run normally, no noise, normal idle as if everything is fine. But ultimately will return.

    Also, the vehicle really seems to run tons better as the outside temperature rises. I could have had this issue forever but the car never saw cold weather so issue never popped up.

    I'm Looking for the order of most likely culprit, I'm now asking what sensor would be sensitive to temperature and be able to cause the misfires. Oxygen sensors? MAF?

    Any insight would very much be appreciated.
    Thanks
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Most likely the issue is with either a spark plug or fuel injector. When did you last replace the iridium spark plugs?
     
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  3. MAW31

    MAW31 New Member

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    Here's the thing pat, after all that I described, a 1200 mile trip, the ability for the motor to shake violently, kick out multiple misfires and then hum moments later, and your thinking the plugs are going to foul and unfoul along with the injectors work then not work in synchrony?

    What are the odds of that happening.

    We're not talking rough running here, we're talking a violent engine shake and rattle.
    Only something systemic can do that to a motor that affects the timing and/or fuel delivery for the entire motor because as quickly as it starts, it can stop. Although sometimes for many minutes. All warmed up or not makes no difference.

    I've got 3 cylinders that report misfires on an engine that ran perfectly for 1200 miles and now in cold weather it doesn't just run rough, it's more of a death rattle. -when it happens-

    I recognize that a start with the basics approach has its merits, but given the nuances and timing of the observations, don't you think you can rule out plugs and injectors by virtue of the observed experience as I described it?
     
  4. bisco

    bisco cookie crumbler

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    if something is changing with temp and rpm, it could be wiring, injectors, intake, throttle and etc.
     
  5. andrewclaus

    andrewclaus Active Member

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    Assuming the check engine light never came on, it's probably something basic and mechanical, not a sensor.
     
  6. MAW31

    MAW31 New Member

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    As noted in the original post, codes were thrown indicating multiple misfires.
     
  7. MAW31

    MAW31 New Member

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    your statement stands up well enough on its own, but given the backstory presented here, you can rule out everything you mentioned since nothing mentioned would stand up to a cause and effect test.

    I.e.: if the throttle body was gummed up, then it would stay gummed up and the observed violent idle would never smooth out. Yet it does, so we can rule out the throttle body as causal to what is observed.

    I.e.: if the wires were bad, then I cannot explain 1200 miles of perfect running followed by super sensitivity to 32 degree temperatures where 3 wires simultaneously all work and then don't work followed by all working in concert again. Possible but far outside the realm of probable.

    But thank you for your input.

    A mechanics true skill is to formulate a list of causes in descending order of probability based on the totality of what has been observed.
     
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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Rather than our continued guessing without the benefit of physical evidence, I think you would need to inspect the condition of the spark plugs, the associated wiring harness connections, the fuel injector wiring harness connections, and whatever sensor wiring connections you can locate.

    For example, a small amount of water in a spark plug well will cause serious misfire that may be attributed to more than one cylinder. If you start with a well-running Prius engine and disconnect one spark igniter, you will see how poorly the engine runs. The impact of that is quite severe.
     
  9. bisco

    bisco cookie crumbler

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    i'm befuddled.(n) perhaps mini vci and tech stream would retrieve the proper codes.
     
  10. edthefox5

    edthefox5 Senior Member

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    I I hope its the throttle body. Probably never ever been cleaned and now the soot is really hurting it since its so cold. MAF too.
    Bad maf would do it but would throw a separate code.

    Has the car ever ran really low on oil like more than 2 quarts on your trip? Multiple misfire reports are very bad as that's usually mechanical like a damaged bottom end. Its the bad vibration that throws off the cam/crank sensor readings. Rotation is not as expected and it throws a misfire.

    Coming from Florida if you get it running I would change the rad and inverter coolant make sure its in good condition because it will get freezing up there regularly.
     
  11. bisco

    bisco cookie crumbler

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    maybe it's just not happy up here. i know i'm not.:unsure:
     
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  12. edthefox5

    edthefox5 Senior Member

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    lol....cold as hell....
     
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  13. bisco

    bisco cookie crumbler

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    you got that right.:mad:
     
  14. andrewclaus

    andrewclaus Active Member

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    Right, forgot that. But to answer your question about a sensor, if a sensor were out of range you'd probably see a code for it.
     
  15. MAW31

    MAW31 New Member

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    Allow me to paint a picture here...
    You're standing in front of car with the hood up and idling smoothly. Then the motor suddenly and violently shakes for up to 3 minutes and then just as suddenly returns to a smooth idle.

    Based on that observation: If you had one item to replace, what would it be?

    I'm headed out to purchase parts today.
     
  16. bisco

    bisco cookie crumbler

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  17. MAW31

    MAW31 New Member

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    Interesting choice
     
  18. andrewclaus

    andrewclaus Active Member

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    One more clarification: Going back to the coolant control valve code, you said you replaced a pump, presumably the engine water pump. Why? The typical fix for the the control valve code is to replace the valve.

    The faulty coolant control valve itself will not affect the engine idle, but a low coolant level might. Did you effectively bleed the coolant loop, and have you been checking the coolant level in the radiator? Does the cabin heat work well?

    It's a stretch, but I would rule out improper sensing of engine temp due to low coolant.
     
  19. bisco

    bisco cookie crumbler

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    just grasping at straws.
     
  20. MAW31

    MAW31 New Member

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    The coolant control valve, pump, and sensor are all housed in one unit. Great questions though. Yes, bled correctly and heater works well. (And yes, it takes some time to do right)
     
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