1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Trouble Persists After EGR, Cooler Replacement

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by BrokenOregonPrius, Feb 20, 2020.

  1. BrokenOregonPrius

    BrokenOregonPrius New Member

    Joined:
    Feb 20, 2020
    4
    0
    0
    Location:
    oreon
    Vehicle:
    2010 Prius
    Model:
    N/A
    Hello all,

    Long time lurker, first time poster. I started having trouble with my 2010 Gen 3 Prius about a year ago. The symptoms seemed to match those described her by posters with EGR problems, and indeed my EGR cooler was blocked with carbon. First I tried cleaning the EGR cooler, intake, and valve as described here. I always need the car to get back to work the next day, and I don't think I got it as clean as I should have, so the problem returned about a month ago. (This is a high-mileage car driven about 90miles each weekday).

    This time I replaced the EGR valve and cooler. I bought the cooler new from Toyota and the valve from RockAuto; it is a WVE-brand part.

    The knocking I had experienced under mild load has not stopped. With EGR valve plugged in, the check engine light is off and the car runs poorly; feels like it is going to shake itself apart. With the EGR valve unplugged, the CEL is on yet the car runs perfectly. I am not getting the misfire code from the OBD2 scanner in either case.

    What on earth is going on? And--am I going to hurt anything if I just continue to drive it with the EGR unplugged?
     
  2. FrankB

    FrankB Member

    Joined:
    Dec 12, 2012
    117
    53
    1
    Vehicle:
    2010 Prius
    Model:
    II
    Did you clean the EGR ports in the intake manifold?
     
  3. BrokenOregonPrius

    BrokenOregonPrius New Member

    Joined:
    Feb 20, 2020
    4
    0
    0
    Location:
    oreon
    Vehicle:
    2010 Prius
    Model:
    N/A
    I’m not sure. I scrubbed out the port where the pipe connects, if that’s what you mean. Is there another EGR port to clean besides that?
     
  4. pjksr02

    pjksr02 Active Member

    Joined:
    Nov 2, 2009
    532
    225
    2
    Location:
    Connecticut
    Vehicle:
    2010 Prius
    Model:
    III
    Just a thought: could a dirty MAP sensor be the cause? With all the oil that gets by the PCV valve, this sensor gets its share, and might be giving the engine control module a false reading.
     
    BrokenOregonPrius likes this.
  5. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,470
    38,103
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Yeah. The EGR passage runs right through, splits into 4, they come come out, one per intake port. Watch @NutzAboutBolts videos.
     
    Tim Jones, pjksr02, fuzzy1 and 2 others like this.
  6. BrokenOregonPrius

    BrokenOregonPrius New Member

    Joined:
    Feb 20, 2020
    4
    0
    0
    Location:
    oreon
    Vehicle:
    2010 Prius
    Model:
    N/A
    I’ll try cleaning those ports; removing the intake is easy enough.
     
  7. BrokenOregonPrius

    BrokenOregonPrius New Member

    Joined:
    Feb 20, 2020
    4
    0
    0
    Location:
    oreon
    Vehicle:
    2010 Prius
    Model:
    N/A
    Not to hard to get to...I’ll try cleaning it at the same time I clean the intake ports. Thank you.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,470
    38,103
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    sorrywereclosed and Tim Jones like this.
  9. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,470
    38,103
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    At each "port" on the intake manifold it's the small opening, 1/4" diameter.

    I found a brush designed for cleaning stainless steel drinking straws worked well. Start it in, then add a little shot of brake cleaner, work it.
     
  10. ArmyChief

    ArmyChief Junior Member

    Joined:
    Apr 4, 2020
    71
    49
    0
    Location:
    North Port, FL
    Vehicle:
    2013 Prius
    Model:
    Persona
    So, how did this turn out?
     
    SFO likes this.
  11. LTChickadee

    LTChickadee New Member

    Joined:
    Dec 26, 2022
    3
    0
    0
    Location:
    Toronto
    Vehicle:
    2010 Prius
    Model:
    III
    I've got the same problem. misfiring on mild acceleration only - Idle and top end runs perfect. Remove the EGR plug from the valve, and the engine runs fine. I've cleaned the EGR cooler, the valve, the pipe, and the intake manifold - including all the 4 small ports. No change, but there was hardly anything there anyways. I've checked the EGR wiring back to the ECM - all good. Same with the MAF wiring. No engine codes either, unless the EGR plug is disconnected. I've checked the plugs - all in excellent shape. I thought about the fuel pressure, the injectors, the coils, and the PCV valve. Not checked these as yet, but all these items (and plugs too) should affect the entire range of engine operation, so not considering these likely culprits of the problem. I'll do a MAF and MAP sensor clean, and see if that helps. The oil catch can is also perhaps something to consider. Will post again if I find out what this problem is.
     
  12. MikeDee

    MikeDee Senior Member

    Joined:
    May 9, 2013
    1,534
    581
    0
    Location:
    San Francisco Bay Area
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Maybe you got a bad EGR valve. Is Rockauto reliable with respect to counterfeit parts?
     
    LTChickadee and Mendel Leisk like this.
  13. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,069
    14,973
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    A couple checks you can do are:

    • Retrieve the car's most recent EGR flow test result (naturally, reconnect the valve first, and make sure you're looking at a test result from after you did that)
    • Perform an active test where you control EGR step position (as you can find described in the troubleshooting steps for P0300)

    If your misfiring is EGR-related and if it does come and go according to when the ECM wants EGR applied, then the good news is, that tends to rule out an EGR valve problem. The valve must be opening and closing at those times if it is causing the misfiring to come and go.

    Even after you've said the manifold EGR passages and four small ports were cleaned, those are still the likeliest suspects for misfiring with that particular pattern. Might be worth a careful second look. But it also won't hurt to get some actual data from the two checks above.
     
    LTChickadee likes this.
  14. LTChickadee

    LTChickadee New Member

    Joined:
    Dec 26, 2022
    3
    0
    0
    Location:
    Toronto
    Vehicle:
    2010 Prius
    Model:
    III
    OK, I've not had much chance to investigate much further, but I did find out some new clues. First, the condition worsens with engine temperature. This threw me for a loop. Its really VERY minor when the engine is cold. That caused me to incorrectly describe the condition. I thought the problem went away when the EGR valve was electrically disconnected, but this is not the case. I had a chance to try this while the engine was warm today, and there was hardly any change in the problem. I thought possibly the problem got worse actually. So, I'm starting to suspect a bad valve. Even though I've measured all the coil resistances in the valve motor, and it seems to be able to turn freely, AND I've replaced it with a used one. If there was a bad valve I would have thought the computer would detect it, but I guess its possible its under open loop control. Will update again with more news when I find out.