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Coil? Plug? Injector? Or bad gas?

Discussion in 'Gen 2 Prius Technical Discussion' started by FazilHussein, Mar 21, 2022.

  1. FazilHussein

    FazilHussein Member

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    2005 Prius
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    II
    Folks,

    My 2005 beast (352,000 km) has finally given me some trouble.

    Heavy snow outside; started to misfire really badly. Limped it home, put some fuel stabilizer in the tank, fired it up the next day, same thing. Read the MIL; P0304, misfire cyl 4.

    Thanks to this wonderful site, I found a TSB (EG 063-05) that detailed a coil/spark plug replacement and applying sealant to the cowl to prevent water ingress. Replaced the coil, cleaned the plug, cleared the code, topped off with premium gas and off we went for another 500km.

    I'm down to two bars of gas and she starts to misfire again; I limp to the gas station, tank with regular...good to go. On the way home, more misfiring.

    So we're down to spark plug or injector. I order both, top with premium and add fuel injector clearer (STP).

    Gave her for an Italian tune up....rough, a little less rough, then smooth. Has been that way for the last week.

    So.....was it bad gas all along? Injector is going to bite me when I least expect it? Plug intermittent?

    Am confused :unsure:

    Does anyone have a similar experience?

    Much thanks,

    Faz
     
    #1 FazilHussein, Mar 21, 2022
    bisco likes this.
  2. PriusCamper

    PriusCamper Senior Member

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    Your oil level isn't low is it? If oil level is good try switching coils around to see if location of misfire moves with the coil or stays in same place.
     
    #2 PriusCamper, Mar 21, 2022
  3. FazilHussein

    FazilHussein Member

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    Hi PriusCamper,

    Checked oil; on the top dot.

    No longer misfiring; going to have to figure out how to break it again ;)

    Wondering if this is related to temp change? Has gone from -20C (I was working on it in the garage @ -10C) to +10C in two weeks; good ol' Canada.

    ~ or ~

    Cyl 4 is weak and premium gas is helping it along.

    Thanks,

    FH
     
    #3 FazilHussein, Mar 21, 2022
    PriusCamper likes this.
  4. bisco

    bisco cookie crumbler

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    i woner if you got some bad gas, and it got stirred up when you refueled
     
    #4 bisco, Mar 21, 2022
  5. FazilHussein

    FazilHussein Member

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    II
    Hi Bisco,

    Seems that way; I'm thinking due to the temp swings and ethanol I ended up with water in the gas.

    1) Misfire restarted when tank was low
    2) Cleared when I tanked
    3) Of course, being a cheap b@stard I tanked with 87 octane (that, and premium was $2.08/L)
    4) Which then sweated out some more water and exacerbated the issue.
    5) Issue cleared using 91 octane (no ethanol) and STP fuel injector cleaner.

    What I can't figure is why only cyl 4? I'd expect random misfire.

    Thanks,

    Faz
     
    #5 FazilHussein, Mar 22, 2022
    bisco likes this.
  6. bisco

    bisco cookie crumbler

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    good question. maybe it is the most worn due to mileage, and most susceptible? idk
     
    #6 bisco, Mar 22, 2022
  7. JahT

    JahT Member

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    If your sounds like this it could just be a bad injector. I replaced coils and plugs but it didn't help my misfire on 1 and 3, but a set of refurbished injectors for $40 fixed the intermittent problem.
     
    #7 JahT, Mar 22, 2022
  8. FazilHussein

    FazilHussein Member

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    II
    Hi JahT,

    Yes, that was the exact noise my poor, poor 17 year old car was making :(.

    Thought it was a goner; almost broke down and bought a new Corolla (red, 6MT, sunroof....like the car...like my $30k better). :)

    I have the injector and spark plug; will take a crack at it this weekend and report back.

    Much thanks!

    Faz
     
    #8 FazilHussein, Mar 22, 2022
    JahT likes this.
  9. edthefox5

    edthefox5 Senior Member

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    Two
    2 things:

    One is I hope you bought an OEM Denso coil as the parts store coils are no good. That's why there half the price.

    The other thing is using your iphone take all the coils off and take a good picture of the spark plug in the well and see if you have any oil leaking into the spark plug well. That's very common too.helps to have the iphone magnifier photo app. I'm using a borescope here since i was scoping out the pistons too.

    Here's a shot of my car's spark plugs wells at 110,000 miles. You can see the oil just starting to fill the well in one photo. New factory gasket was $30 when i bought mine 3 years ago.

    It's easy to take the valve cover off and a great time to replace the pcv valve out too. Many people have busted a hole in the valve cover using the wrong wrench/technique trying to remove the pcv. Much easier if cover off.
    And you get to check the chain for wear. And also see how your engine oil is taking care of the top end.
     

    Attached Files:

    #9 edthefox5, Apr 7, 2022
    Last edited: Apr 7, 2022
  10. FazilHussein

    FazilHussein Member

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    Location:
    Perth, Ontario, Canada
    Vehicle:
    2005 Prius
    Model:
    II
    Hi Ed,

    You caught me :D I did cheap out and buy the amazon specials.

    BUT!!!

    It turned out to be the injector; once I replaced it, running normal again....zero misfires.

    Have put 3k on it since, regular gas; running like a top.

    I did replace the PVC at the same time as the plugs; thankfully did not break anything.

    Good point on the valve cover gasket; it will be part of my once over this summer.

    Thanks,

    Faz
     
    #10 FazilHussein, Apr 20, 2022
    JahT and bisco like this.
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