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

Which cylinder is which?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Jon Schro, Sep 30, 2021.

  1. Jon Schro

    Jon Schro New Member

    Joined:
    Sep 8, 2021
    19
    4
    0
    Location:
    Middletown, Connecticut, USA
    Vehicle:
    2010 Prius
    Model:
    II
    Sorry for the newbie question, but how do I know which cylinder is which?
    I'm getting a misfire in cylinder #2. Is that the second one from the left, or is that the second cylinder in the firing order shown here?

    [​IMG]
     
    #1 Jon Schro, Sep 30, 2021
  2. xliderider

    xliderider Senior Member

    Joined:
    Apr 19, 2012
    7,848
    3,102
    0
    Location:
    Honolulu, HI
    Vehicle:
    2011 Prius
    Model:
    Three
    Second from the left. How many miles, and what year is your car.

    Posted via the PriusChat mobile app.
     
    #2 xliderider, Sep 30, 2021
    Raytheeagle likes this.
  3. Jon Schro

    Jon Schro New Member

    Joined:
    Sep 8, 2021
    19
    4
    0
    Location:
    Middletown, Connecticut, USA
    Vehicle:
    2010 Prius
    Model:
    II
    Thanks. 2010, 190k miles. P0302 code. Engine knocking. Coolant level is low. I'm worried about a head gasket failure.

    Got it all opened up to access the spark plugs now. I bought a leak down tester on amazon and I'm gonna try to figure out how to run the test on cylinder 2.

    Would appreciate any further tips while I got it opened up. Thanks!
     
    #3 Jon Schro, Sep 30, 2021
  4. xliderider

    xliderider Senior Member

    Joined:
    Apr 19, 2012
    7,848
    3,102
    0
    Location:
    Honolulu, HI
    Vehicle:
    2011 Prius
    Model:
    Three
    Sounds like head gasket failure, usually between cylinder 1 and 2. Perform the leakdown test on all 4 cylinders, not just on cylinder 2.

    Posted via the PriusChat mobile app.
     
    #4 xliderider, Sep 30, 2021
  5. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,691
    38,232
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Visual aid:

    upload_2021-9-30_11-49-19.png

    How many miles on the car, and has the intake/egr been cleaned?

    Info in my signature.
     
    #5 Mendel Leisk, Sep 30, 2021
    fuzzy1 likes this.
  6. Jon Schro

    Jon Schro New Member

    Joined:
    Sep 8, 2021
    19
    4
    0
    Location:
    Middletown, Connecticut, USA
    Vehicle:
    2010 Prius
    Model:
    II
    Is it okay to do a leak down test with the engine cold? I can't really run the engine long enough to warm warm it up.
     
    #6 Jon Schro, Sep 30, 2021
  7. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,691
    38,232
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Don't see why not, but I'm clueless. You're basically trying to see how and where air's escaping, should work with cold engine. The rule I've heard is the cylinder should be at TDC of the compression stroke. Now how you determine it's the compression stroke is a little tricky. And is it critical, or would either TDC (compression or exhaust) give sim results. I defer to:



    He has trouble with the gauges, but gives tips on how to determine compression TDC, and he does ultimately nail the problem, gauge issues aside.
     
    #7 Mendel Leisk, Sep 30, 2021
  8. Jon Schro

    Jon Schro New Member

    Joined:
    Sep 8, 2021
    19
    4
    0
    Location:
    Middletown, Connecticut, USA
    Vehicle:
    2010 Prius
    Model:
    II
    So... First I pulled the spark plugs out, and the spark plug from Cylinder #2 (the one misfiring) was black and oily.

    Then, I ran a leakdown test on each cylinder. #1 and #2 were good, but #3 and #4 both leaked around 60%. I listened carefully, and really it seemed like the leaking sound was coming from the same cylinder which was being tested at the time. Nothing from the dipstick hole, no bubbles in the coolant. Am I doing this right? I removed, reattached, and reran the test several times to make sure it had a good seal. I also tried turning the engine down 360 degrees to get back to TDC again just in case I was on the wrong stroke.

    I suppose cylinder #3 and #4 are leaking into each other? (even though the sound seemed to be coming from the cylinder being tested rather than the adjacent cylinder?)

    Any thoughts on what this all means?
     

    Attached Files:

    #8 Jon Schro, Sep 30, 2021
  9. xliderider

    xliderider Senior Member

    Joined:
    Apr 19, 2012
    7,848
    3,102
    0
    Location:
    Honolulu, HI
    Vehicle:
    2011 Prius
    Model:
    Three
    Black and oily spark plug is from oil fouling, the intake manifold sucks up oil from the PCV valve vented from the lower engine block.

    Maybe you should check your PCV valve while you have some parts off. Since the cylinder leakdown was good, the oil isn't coming from the crankcase side of the rings. The intake manifold is pretty easy to remove, compared to the windshield cowl and coils/plugs.

    Posted via the PriusChat mobile app.
     
    #9 xliderider, Sep 30, 2021
  10. Jon Schro

    Jon Schro New Member

    Joined:
    Sep 8, 2021
    19
    4
    0
    Location:
    Middletown, Connecticut, USA
    Vehicle:
    2010 Prius
    Model:
    II
    That makes sense, but I already cleaned the intake and replaced the PCV valve. Anything else I should try?
     
    #10 Jon Schro, Oct 2, 2021
(You must log in or sign up to post here.)