2014 Prius hybrid engine misfire? code P301,P302, P304

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Adrian Valerio, Jul 17, 2024.

Tags:
  1. Adrian Valerio

    Adrian Valerio New Member

    Joined:
    Jul 17, 2024
    2
    1
    0
    Location:
    92805
    Vehicle:
    2014 Prius
    Model:
    Four
    Hello fellow Prius owners,

    I'm reaching out for some assistance with my 2014 Prius 4.

    In March 2022, my catalytic converter was stolen. I initially wanted to replace it with an original one from Toyota, but they were back-ordered, and I believe they still are. After waiting for about 8 months with my car parked, I opted for an aftermarket catalytic converter from eBay for around $140. I had it welded at a muffler shop, which caused the check engine light to come on due to the O2 sensors. However, I wasn't too concerned since I knew the cause, and the car drove without issues. At that time, the car had about 120,000 miles.

    Now, with the car at 155,000 miles, I experienced a problem one morning. After starting the car, the engine made a loud knocking noise that lasted for a minute or two but then went away, and the car performed well with no power loss. When I scanned for codes, I found P0301, P0302, and P0304. I replaced the spark plugs and ignition coils, thinking it might need a tune-up due to the mileage. The car drove well for about 30 miles over two days, but the engine knocking has returned intermittently and stops once the engine warms up. The car drives fine otherwise, so I'm unsure what the issue could be or where to start.

    Any help would be greatly appreciated.
     
    #1 Adrian Valerio, Jul 17, 2024
  2. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    11,546
    2,026
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    Read all about the generation 3 head gasket issue and then when you had the plugs out you should have looked at them with a magnifying glass the Park that's inside the engine the insulator and look for the tiny microscopic droplets touch your finger to it run it under your nose or touch your tongue and you'll be testing and smelling and tasting ethylene glycol more than likely and cylinder one or two plugs out borrow an inspection camera or buy one and look at the head gasket from inside of the engine and see the water droplets built up around the head gasket area where it meets the block and head together and then you know what you have the fires getting put out by water vapor etc It's possible it's not happening but more than likely look carefully good possibility. Expensive fixes generally speaking
     
    #2 Tombukt2, Jul 17, 2024
    Brian1954 likes this.
  3. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,485
    50,772
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    have you done an egr circuit cleansing?
     
    #3 bisco, Jul 18, 2024
  4. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    9,261
    5,631
    7
    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Head gasket
     
    #4 rjparker, Jul 18, 2024
    Brian1954 likes this.
  5. Adrian Valerio

    Adrian Valerio New Member

    Joined:
    Jul 17, 2024
    2
    1
    0
    Location:
    92805
    Vehicle:
    2014 Prius
    Model:
    Four
    no, all I have done is change out the spark plugs and ignigtion coils.
     
    #5 Adrian Valerio, Jul 22, 2024
    bisco likes this.
  6. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,485
    50,772
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    it's important to clean the egr at that mileage, but you might want to get a hg test first.
     
    #6 bisco, Jul 22, 2024
(You must log in or sign up to post here.)