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Very rough idle, several DTCs, odd smelling exhaust

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bigger, Apr 16, 2017.

  1. Bigger

    Bigger Junior Member

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    I replaced the MAF. No change. I'll start looking at coils and plugs tomorrow. Thank you all for the continuing advice.
     
  2. edthefox5

    edthefox5 Senior Member

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    Yeah it didn't throw a maf code.

    Be aware we have seen quite a few Prius with blown bottom ends from low oil events that start out with
    misfires that move around. So much bottom end vibration it distorts the cam/crank sensor data and is interpreted as lack of fire in a cyl by the engine ecm. Usually the rod wrist pin bearing on the piston fails from low oil level lack of splash. Lack of splash starves the top bearings first. Starts thumping in the motor then turns into a knock then turns into smoke hiss boom. Toughest little motor ever but will not tolerate no oil.
    For some reason its always piston #3 that fails first. Always keep the oil at the full line.

    But probably needs all new cops and plugs.Use only OEM cops.
     
    Bigger likes this.
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Considering the engine has 225K miles, and since you have Techstream, I suggest you also check engine compression. You can use Techstream to spin the engine at the correct speed for a compression test, so you just need the compression pressure gauge that will screw into a cylinder spark plug hole. That will help you to determine whether there are any mechanical faults with the engine. As the engine is spinning with three spark plug holes open and one filled with the gauge, it should spin pretty smoothly if it doesn't have mechanical issues.

    Cylinder compression spec is 128 psi, no more than 14 psi variation across cylinders, and minimum pressure of 99 psi. If the cylinder compression is reasonably even across cylinders and at or near spec, then you can feel comfortable that the misfire issue is due either to a spark issue or a fuel issue. Hence that would lead you to check the spark igniters, spark plugs, and then finally fuel injectors if the igniters/plugs are good.
     
    #23 Patrick Wong, Apr 20, 2017
    Last edited: Apr 20, 2017
    Bigger and Eclipse1701d like this.
  4. Bigger

    Bigger Junior Member

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    While I sincerely hope that this is not the problem, how can an earnest but inexperienced mechanic diagnose this? Bottom end won't show up in a compression test, as I understand it. I'm not skilled, equipped or budgeted to pull the motor and mike the crankshaft.
     
  5. Bigger

    Bigger Junior Member

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    I'll see if my local Auto Zone loans compression testers. otherwise I'll start haunting used tool sites. Thank you for the advice.
     
  6. edthefox5

    edthefox5 Senior Member

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    Not the crank that will need a mike its the piston rods that go first. Go on youtube look up "prius Inspection mode" and you will see how to make the car idle endlessly giving you time to listen to the engine in various spots. With car idling lay under the front of the car and listen to the bottom of the engine for low frequency rumble or thumping.

    if you ever ran the oil so low it turned the check engine light on you are a good candidate for blown bottom end.
     
  7. Bigger

    Bigger Junior Member

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