Random misfires

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Noobprius, Jan 25, 2017.

  1. Noobprius

    Noobprius Junior Member

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    Hey guys. My 2006 prius has random miss fires in the first and third pistons. The throttle body has been cleaned and the spark plugs have been changed back in august of last year, with no change. I am guessing that the ignition coils are bad, so how do you check them to see. Also, ig you have any other suggestions on what it could be, feel free to tell me please.

    Edit: I have been told that these two pistons also have low compression.
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    #1 Noobprius, Jan 25, 2017
    Last edited: Jan 25, 2017
  2. andrewclaus

    andrewclaus Active Member

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    You answered your question--the pistons have low compression. A good mechanic should be able to diagnose and tell you what the solution would cost, but it's doubtful it'll be cost-effective to repair. Is this a high-mileage engine that burns oil? It sounds like there might be good value in purchasing a low-mileage salvaged engine. Consider the health of the hybrid battery (over ten years old now?), the condition of the rest of the car, and its market value when making your decision. Your expensive catalytic converter may have issues soon, too, if the engine is in poor health.
     
  3. Noobprius

    Noobprius Junior Member

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    The motor does have 201,000 miles on it, but as far as I can tell, no oil is being burned. I will have to look again to make sure. I was told by the previous owner that the hybrid battery has been replaced fairly recently (I have no repair records and idk how to check. Is there something on the battery?)

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  4. andrewclaus

    andrewclaus Active Member

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    These engines are well known to start burning some oil sometime after 150K miles, so it would be good idea to check the oil level frequently, say every other fill-up.

    Is the engine running rough, and/or noisy?

    Without records, you'll have to look at the battery. Some aftermarket battery cases are painted a bright color, easily seen after some minor disassembly in the luggage compartment. Rebuilds will have discontinuous serial numbers on the 28 battery modules, and you'll have to open the case to inspect that, a bit more involved. High voltage hazards exist, so be sure you know what you're doing there. The original modules will have a year code compatible with the model year--search this forum for codes if needed. None of this is worth it if the battery is working fine, and most are. I mention it as a possibly expensive repair in the coming years.
     
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  5. Noobprius

    Noobprius Junior Member

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    The motor runs rough on idle only. Since it is winter, the motor tends to idle a bit higher, so the sounds aren't there, but there is a shake in it and a rattling sound kinda, idk how else to describe it. And thank you for the battery info.

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  6. andrewclaus

    andrewclaus Active Member

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    If the oil was ever run low, the bottom half of the engine could have seen some damage. That could account for noise and shaking. If it's more noticeable from under the car (be careful!), that's probably it.
     
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  7. Augustus88

    Augustus88 Junior Member

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    It is normal for the car to shake from the engine during the initial warmup cycle, or when the engine is charging the battery at an idle stop, for example, when sitting in a parking lot with the AC on for a long time, and the battery drains to two pink bars.

    If it is shaking when in neutral, or when accelerating, you have a genuine misfire problem.
     
  8. edthefox5

    edthefox5 Senior Member

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    What you describe is classic blown bottom end of a Prius. There's so much bottom end vibration its confuses the crank sensor and it will throw multiple misfires.
    The car should never shake no matter what its doing at least mine doesn't. The rattle your hearing is the piston rod bearing.
    Usually caused by running a car that eats oil low on oil. Throws a check engine light from oil starvation. Previous owner knows this and you got boned.

    And assuming the traction battery has been replaced because the previous owner said so is silly.

    Anyway go on youtube and look up PRIUS INSPECTION MODE and you'll be able to get the engine to run continuously. get under the front of the car under the engine while its running and listen for disturbing sounds like banging and thumping and vibration.
     
  9. Noobprius

    Noobprius Junior Member

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    @edthefox5 yeah, I agree with you on the getting boned part. However, it's a car I picked up for 2100, and when the car KBB for atleast 2500, I say overall, it's not a bad deal. However, the previous owner was a company that I worked for and other family members work for now. It is a family company, so I trust them on the whole main battery.

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  10. Noobprius

    Noobprius Junior Member

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    It does have awful compression however. The compression has been tested, and shows low compression, especially in the first piston.

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  11. b100

    b100 Member

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    I think its time for a new engine, or used one.
     
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