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Gen 2 shuddering and throwing misfire codes.. could use some help

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Wisco, May 21, 2022.

  1. Wisco

    Wisco Member

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    So I bought a 2005 with 200k miles a few weeks ago, everything seemed fine at first. Had some shuddering in the past week, and it got significantly worse today and threw misfire codes. Seems to be worst at low RPMs.

    Codes: P0300, P0301, P0303 (misfires in cylinders 1 and 3. Also P0607, but that’s probably just because the exhaust is funky from the misfires.

    So, the obvious approach seems to be trying new plugs and air filter, then ignition coils, maybe clean the MAF and other stuff that could be gunked up. I’m really hoping it’s not the head gasket, and fortunately failures seem rare in gen 2s. Coolant isn’t low, oil doesn’t look funky.

    I haven’t been driving this car much. And in my Gen1 the 12v battery was the source of 80% of my problems. Is there any way a weak 12v could cause misfires?

    I checked it after 2 hours of driving and it’s at 12.5 volts. Not terrible, but I’d expect 12.6-7 in that situation.

    I’d really appreciate suggestions for how to chase this down. I spent more than I’d like on this car, and the possibility of a major problem has me sick to my stomach.
     
  2. Another

    Another Senior Member

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    I’m sure others on the forum with much more experience will have specific tips on the implications of the codes and the subcodes but in the interim I’d download the service history on the car from Toyota for free or get a carfax report to see what’s been done with it if they used a dealer or other retail mechanic.

    Logged Out My Vehicle Page | Toyota Owners
     
  3. jerrymildred

    jerrymildred Senior Member

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    It may be that those are the original plugs. If so, misfires at about 200k miles would not be surprising. I think you're starting in the right direction.

    It could also be dirty fuel injectors.
     
  4. edthefox5

    edthefox5 Senior Member

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    Problem with chasing misfires on this car is the factory denso coils are expensive at $100 each. But they work. The parts store cops suck for $50 each. So throwing good cops at it gets expensive.

    Unfortunately rolling misfires are sometimes caused by blown engine rings or bearings gone. People tend to never check the oil in a Prius and they start eating oil so by the time the check engine light comes on to tell you engine is dry its too late.
    Really common on this site. Nobody checks there oil especially if they get the oil changed at the dealer.

    Pull the plugs see if there's oil on them. That's pretty telling If so if it was me I would do a compression test on all 4 cylinders.
    In fact I would do a compression test first before spending a dime on this car.

    Could be cat is clogged up but that's caused by bad oil eating.

    And 12.5 volts at the front jump point is just about perfect. A perfect 12 volt in a G2 lives at 12.6 volts at the jump point.
     
  5. Stevewoods

    Stevewoods Senior Member

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    Personally, I would clean the MAF first -- it's easy enough. And, as suggested, pull the plugs and see what they look like. But, my daughter's car had the pretty much the same issue -- except we did not pull any codes -- and cleaning the MAF made it all go away.