2012 Prius Two. Cylinder misfire P0303.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by YuriR, Mar 17, 2020.

  1. YuriR

    YuriR New Member

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    I bought a used 2012 Toyota Prius with 133k miles. Everything was well for the first three hundred miles.
    I got a check engine light and there was knocking at the start of the engine one night when it was around 40 degrees outside.

    Check the codes and found P0303 Cylinder Misfire in cylinder 3.
     
  2. YuriR

    YuriR New Member

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    I found this forum and videos from NutzAboutBolts. Replaced spark plugs.

    oldPlugs.jpg oldPlugsNewPlug.jpg

    Erased the codes, misfire is still there, but not in the maintenance mode. Only on IDLE and low RPMs.
     
  3. YuriR

    YuriR New Member

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    Then I decided to take apart the intake manifold, throttle body, and EGR pipe. They looked not very bad. Cleaned them with brake cleaner.
    Also, I found some oil in the bottom of the throttle body.
    All of that didn't help much. Erased the code again and the engine is started working fine but misfire came back with no codes. I drove the car about 100 miles with no codes popped up.

    By the way, I also swapped the ignition coils from 1 to 3 and 2 to 4 just to eliminate the coil issue if there will be a code from a different cylinder.

    EGRPipe.jpg intakeManifold.jpg throttleBody.jpg intake.jpg intake2.jpg
     
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  4. YuriR

    YuriR New Member

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    Very next day I pulled fuel injectors out to check them, my friend suggests that there might be a problem with them that causing the misfire.
    They look nasty, especially number three. I put them in the order they were installed.
    The first injector I already wiped before taking the picture.
    I wasn't able to clean the inside, just wiped them from the outside. Also swapped the injectors 1 to 2 and 3 to 4.
    No codes for about 50 miles.
     

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  5. YuriR

    YuriR New Member

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    With no codes, I gave up and got the car into the nearest Toyota shop for a professional diagnostic.
    They said there is a bad ignition coil on cylinder four, they also got the code P0304.
    I bought a new ignition coil from them and replaced that. Erased the codes and turn the engine on, still see misfire on low RPMs and IDLE for a little while. The guy from the shop said if there is no code, it is fine. He doesn't notice misfiring, but I remember how it was running before the issue.
     

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  6. YuriR

    YuriR New Member

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    I got the code back yesterday. P0300, P0304. I guess that might be the fuel injector on cylinder 4 now since I swapped 3 and 4 while taking them out a week ago.
    I remember when I took the fuel rail out of the fuel injectors I had a lot of gas came out since that is pressurized. I started looking for a fuse that powers the fuel pump to run the engine and pull out the fuse to empty the fuel rail to minimize the spill.
    Can anyone help me locate the fuse or relay?
     

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  7. YuriR

    YuriR New Member

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  8. fotomoto

    fotomoto Senior Member

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    What does the oil on the dipstick look like? Milky color?

    Coolant at the proper level?
     
  9. YuriR

    YuriR New Member

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    Coolant is in low level, I had a spill when disconnecting the throttle body.
    Have not noticed any significant level drop.
    Dip stick, going to attach a picture
     

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  10. Ed Beaty

    Ed Beaty Active Member

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    Hard to tell if that white-ish area is 'milky' or just a reflection. Also, your oil is WAY TOO LOW...
     
  11. YuriR

    YuriR New Member

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    Can this be more visible?
     

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  12. Grit

    Grit Senior Member

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    Was a compression test test done before? And was coolant low when you first notice the excess knocks?
     
  13. YuriR

    YuriR New Member

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    Compression test has not been done yet. Coolant level was at low level when I bought the car. Now it is about the same as it was. What progression is for the coolant level when there is a blown head gasket?
    Can anyone help with locating a fuel pump fuse?
     
  14. cnc97

    cnc97 Senior Member

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    Just pull the fuel pump relay from the fuse box under the hood. The injectors will then function until the fuel remaining is burned off. Or pull the entire rail off the car before removing the injector(s). That way you can direct the fuel into a drain pan.
     
  15. YuriR

    YuriR New Member

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    Can you help me with locating that relay?
     

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  16. cnc97

    cnc97 Senior Member

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    It’s marked 20A EFI MAIN
     
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Did you thoroughly clean the EGR passageways in the intake manifold? Also, if I'm reading right: you haven't cleaned the EGR valve or cooler? Until that is all done, the EGR continues to be partially clogged, probably moderately so with those miles.

    Good thread:

    EGR & Intake Manifold Clean Results | PriusChat

    Another:

    Oil Catch Can, Eliminate that knock! | PriusChat

    Some tools worth having:

    E8 Torx socket (mandatory)
    E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
    3/8" ratchet wrench, regular and long handle, flex head, you can never have enough (or 1/2 plus reducer)
    1/4" ratchet wrench, or 3/8" to 1/4" reducer
    Ratchet extensions: you can never have enough
    Long needle nose piers, straight and bent tip
    Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
    Torque wrench (3/8" and 1/4" both good to have)
    Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.

    Comment regarding clamping of coolant hose, mentioned and or shown in videos:

    1. When removing the intake manifold for cleaning, you do need to lift the throttle body off the intake manifold. Still, the coolant hoses connected to the throttle body have ample slack, enough that you can leave them connected, and just tie the throttle body to something adjacent, say the inverter wiring harness.

    2. When removing the EGR cooler, removing coolant hoses is necessary, but if you drain 2 liters/quarts from the radiator drain spigot prior (into a clean container), the coolant level in the system will be dropped below the EGR componennts, and you won't spill anything. Just be sure to not tip the cooler when lifting it off (and catch the rear gasket): there are a few tablespoons of coolant trapped at the lower back corner.

    Pour that into your previous drained coolant, and when done pour it back into the reservoir. If you've got the coolant bleed bolt (2010, 2011 model years), leave it open while pouring the coolant back in, till coolant starts coming out. For later model years, leave the topmost coolant hose on EGR disconnected till coolant starts coming out. Also, might help to burp the main radiator hose as you pour the coolant back in.
     
  18. YuriR

    YuriR New Member

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    Thank you all for your help. I appreciate Mendel Leisk for the detailed post that will be very helpful for me.

    Since I had the code P0303 and after I swapped the fuel injectors from 3 to 4. Then I got the code P0304.
    I have cleaned all of the fuel injectors this morning with a 9v battery and some brake cleaner. They were spraying not bad. I also installed them back in order as 4-3-2-1. So if I get a code as cylinder 1, then I might need to replace the fuel injector.
    When I removed the EFI fuse the engine didn't run out of fuel, it just shut the engine right away with the check engine light as hybrid battery maintenance and when open the fuel rail there was still some fuel pressurized. I guess EFI is Engine Fuel Injectors and not the fuel pump.

    Turn the engine on after cleaning without removing the codes, the engine started very rough, like all of the cylinders misfiring.
    Clearing the codes helped right away, the engine is still running as before with little knock.

    I think the next step will be as Mendel Leisk posted is to clean the EGR valve and cooler. I also bought a compression test kit so during that cleaning procedure I will check the compression in the cylinders.

    I have a question regarding the compression test. What fuse is used to disable the ignition coils, and I will remove EFI MAIN fuse for disabling fuel injectors. IS that right do I need to disable both components (fuel injectors and ignition coils) for the compression test?

    During the compression test, will I need another battery or charger (I don't have any of these)? Will my battery dies or hybrids have support from the electric motor's battery?
     
  19. Mendel Leisk

    Mendel Leisk Senior Member

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    Good sleuthing. (y)

    Starting the engine uses the hybrid battery. It wouldn't hurt to have a smart charger hooked up, after the testing.

    I've heard fuel injector O-rings are very touchy?

    In the attachment it says "do not twist the O-ring". Maybe better wording would be "don't get the O-ring twisted"? I'd think a little twisting of the injector as it goes in would actually help avoid rolling the O-ring.

    It mentions "spindle oil or gas" as lubricant. Googling a while back, a lot of people mentioned silicone dielectric compound.
     
    #19 Mendel Leisk, Mar 21, 2020
    Last edited: Mar 21, 2020
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  20. YuriR

    YuriR New Member

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    I used silicone lube and put everything back in. There was not enough room to pull the fuel rail far away. There are no leaks at least.
     
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