Rough with low throttle or during maintaining speed.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by tjernagel, Apr 15, 2023.

  1. tjernagel

    tjernagel Junior Member

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    2010 Prius - Last week ended up with P0302, P303 and P304. Misfire detected on three cylinders and Joyce reported a noise when the engine started up. Although the codes were recorded the car was running fine when she got home...

    Replaced ignition coils, plugs, injectors, mass airflow sensor, cleaned the throttle body and replaced the transmission fluid. The plugs looked really good. All codes are clear with no permanent codes stored. The transmission fluid looked really good with no smell. The CV joints are good and the car has just over 212,000 miles on it.

    Car idles fine and under "power" runs well. But while moving and if light throttle is introduced or while it's being maintained on cruise control you can feel what seems to be the engine cutting out. It's not jerky or severe but it can be felt. Put more power in or take all power off makes it go away.

    I've driven it around 75 miles with this condition and there are no codes being recorded.

    I don't have a clue. I'm don't have a clue what is causing it. Any suggestions?
     
    #1 tjernagel, Apr 15, 2023
  2. bisco

    bisco cookie crumbler

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    wild guess, fuel pressure?
     
    #2 bisco, Apr 15, 2023
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    How long have you had it, since new, or?

    Have you ever cleaned the EGR components, and the EGR passages in the intake manifold?
     
    #3 Mendel Leisk, Apr 15, 2023
  4. ChapmanF

    ChapmanF Senior Member

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    I would definitely look at those manifold passages, after this description.
     
    #4 ChapmanF, Apr 15, 2023
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  5. tjernagel

    tjernagel Junior Member

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    After I posted I read the posts on the EGR. It's the first thing on my plate in the morning. Thanks for all the great information.
     
    #5 tjernagel, Apr 15, 2023
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  6. tjernagel

    tjernagel Junior Member

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    Fuel pressure. EGR is going to be checked tomorrow. The system has never been opened since we bought the car new in 2010... This is the first maintenance issue we have had. It's been a great car for Joyce.
     
    #6 tjernagel, Apr 15, 2023
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  7. bisco

    bisco cookie crumbler

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    i agree on the egr, do that first
     
    #7 bisco, Apr 16, 2023
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    With OP's miles, I'd make head gasket first priority. Consider leak-down test and/or boroscope inspection of the cylinders while the cooling system has pressure applied (looking for tears of coolant, suspiciously clean piston tops). Running rough on cold-starts can be coolant in the cylinders, head gasket already leaking.

    Cleaning the EGR now won't "reverse" a head gasket failure. But once the head gasket is assessed (and/or replaced), EGR cleaning should be priority, to avoid another blown head gasket.
     
    #8 Mendel Leisk, Apr 16, 2023
  9. tjernagel

    tjernagel Junior Member

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    Cleaned the EGR system from the valve into the intake manifold. Dirty, dirty, dirty, dirty... :) It's back together now and the problem is gone. Thanks for the help! Not a big fan of Harbor Freight but found this brush set which worked perfectly for cleaning the intake and stainless steel EGR tube. I ended up picking up two because I needed a second extension to reach all the way into the bore of the intake.

    https://share.icloud.com/photos/08ciMrCxZ0Xgv8vmDWojx9oFA
     
    #9 tjernagel, Apr 16, 2023
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  10. ChapmanF

    ChapmanF Senior Member

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    You may want to clean up the cooler behind the valve too, at some point, but yes, the symptoms you reported were likely caused by the differently-plugged manifold passages, which you've now cleaned.
     
    #10 ChapmanF, Apr 16, 2023
  11. tjernagel

    tjernagel Junior Member

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    I couldn't get the gaskets today so I am planning on taking it apart again in a week or two not only to put the new gaskets on but to clean the cooler. The intake was pretty simple, the cooler looks more challenging. :)
     
    #11 tjernagel, Apr 16, 2023
  12. ChapmanF

    ChapmanF Senior Member

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    That it is.
     
    #12 ChapmanF, Apr 16, 2023
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    See first couple of links in my signature for EGR, some tools and tips.
     
    #13 Mendel Leisk, Apr 17, 2023
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