2011 Prius P0303 misfire

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by rtstrider, May 15, 2017.

  1. rtstrider

    rtstrider New Member

    Joined:
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    Location:
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    Vehicle:
    2011 Prius
    Model:
    III
    After extensive time with the mechanic they stated this is either a valve or piston ring issue on cylinder 3. He said he would have to take the engine apart to further diagnose and we would be looking at at least a grand just to diagnose. Said he would have to take the head off and pour oil in it to see if that's where the leak was coming from. He said with as many miles are on the car he's not sure if it'd even be worth fixing. By the time he diagnosed the issue and possibly fixed it we could purchase another used Prius for the same cost. The plug looked like the threads/electrode were dipped in a vat of oil. I tried a piston soak with MMO overnight. Put around 3-4 oz in cylinder 3 only. Next morning it was bone dry. So the mmo leaked past the piston. The engine was turned over without a plug in cylinder 3 and no MMO shot out of the cylinder either. Put a denso plug back in there and took it down the road. No smoke or anything. So I added a pint of MMO, drove around 500 miles, and changed the oil last night. I was originally using 4.5 quarts Mobil1 high mileage 0w 20. I changed to supertech high mileage 5w 30 (3.5 qt's) and 1 qt Marvel Mystery Oil. Going to run this for 3k miles or until the oil looks dirty and do the same for the next couple of OCI's. Honestly this is a last ditch effort as I do not want to tear the engine apart. Hoping this may help!
     
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  2. johnamerc

    johnamerc Junior Member

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    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Good afternoon rtstrider, did you ever solve your issues?

    2010 III here w/271K miles now. The engine uses 1 qt of oil every 1,000 miles or so. I had trouble in November with the dreaded EGR valve code P0401. Ignored it. Got ready for a trip to GA from here in NY and severe missing and P0303 appeared. Had spark plugs replaced @ dealer (which had been the originals) and Voila! issue fixed. 5,000 miles later no miss to speak of.
    In April I decided to tackle the EGR issue as my annual state inspection was due in May and found out that there was an extended EGR warranty w/unlimited mileage that expired March 31, 2017. Then called Toyota and they basically said, "tough"
    I Replaced the EGR valve using a local non Toyota mechanic. He found the EGR cooler was caked w/ crud and spent extra time cleaning it. The miss returned with a vengeance. It happens when the engine is warm.
    The first seven minutes from a cold start are heaven, then ugh!
    P0303 code had returned.
    The local mechanic showed me the spark plug and it was the dirtiest nastiest plug I ever saw. Replaced plugs again after only 30K miles or so. No relief from miss. He switched coils and P0303 continued to return. He checked valves and did some sort of carbon cleaning and missing mostly stopped. He wanted me to drive 30 miles before giving me a new inspection sticker. After 50 miles still no codes. Got my new inspection sticker. Yeah! Drove to my sons house in PA and after 100 mile miles . . . check engine light back on. Another ugh! My indicated MPG after returning home was 51.2 using conservative driving. 55 or higher was normal for me in the summer originally and has been drifting lower.
    Missing getting worse. Now P0303, P0335, P0420. Mechanic switched injector 3 w/2 and misfire did NOT follow along to cylinder #2. Reset the codes. 25 miles later no codes yet.

    If I push power mode the car misses less.

    If I pulse drive e.g. if speed posted @ 45 I accelerate fairly briskly to 52 ish and go back to electric mode letting speed drop to 42 or so then repeat the missing is minimal.

    Problem is especially noticeable on transitions between electric mode and gas and viced versa.

    Aggressive acceleration and up hill sections eliminate the miss.

    Contemplating next step.

    More later.

    John
     
  3. johnamerc

    johnamerc Junior Member

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    Model:
    Prime Plus
    Oh, by the way I rented a 2017 Ford Fusion Hybrid while mine was in the shop. Drove to GA and back with 49.5 MPG on display. Had bumped tire pressure to 40 all the way round and kept most of the driving @ 65 or lower. Very nice ride even compared to a 2018 Prime that I tested. Quieter, great handling and comfortable yet a little snug in the front seat.
     
  4. JC91006

    JC91006 Senior Member

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    Vehicle:
    2010 Prius
    Model:
    V
    Well not many options left here.

    1. Replace engine with one that has less miles and clean EGR system.
    2. Buy a new Ford Fusion.

    Any other option will just empty your wallet a little at a time.
     
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  5. johnamerc

    johnamerc Junior Member

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    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    272,009 miles. now. using PWR mode. Hybrid battery now stays @ perceptively higher levels of charge. Reach full charge more often and rarely down to 3 bars. Plenty of hills here. Used Chevron fuel treatment for last tankful and will now use Lucas fuel treatment (3 oz/10 Gallons) for next 8 tankfuls or so. Less missing w/PWR mode. Avoiding cruise control helps. Seems a bit better overall. Avoiding gradual transitions especially in low power/acceleration demand situations. Drive routes that avoid low speed stop and start. Driving uphill seems normal.
    Check engine light comes on every day or two. Then goes off within 1 day. OBD II ordered. Will watch codes and missing more closely when that arrives. Guessing Auto Zone is tired of seeing me. And expensive to stop @ mechanic for a daily readout.
    Drove a 200 mile round trip yesterday and return today. All was fine.
    Was hoping for 500 K. Seeming unlikely these days. Taking 1 day @ a time.
    MPG remains around 50 w/ conservative driving techniques down from around 55 when new. Would like to get a Prime . . . not this year. Also rear headroom in the Prime/Gen 4 an issue for taller people. A step back in the rear sear to Gen 2 imho.
    More later.

    John - around 804,000 total hybrid miles. 2001 gen1 345,195,miles. 2004 V, 2010 II, 2010 III and a few rentals over the years.
     
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  6. mjoo

    mjoo Senior Member

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    Vehicle:
    2010 Prius
    Model:
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    I think the fuel pump is something that commonly starts to go at your mileage

    Pixel XL ?
     
  7. johnamerc

    johnamerc Junior Member

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    Prime Plus
    The fuel pump on my '01 Prius went @ 288,000 miles. Thanks for the reminder. Now 276,000 miles
     
  8. Shoes

    Shoes New Member

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    Vehicle:
    2012 Prius
    Model:
    Two
    I’m the same problem on my 21 prius and jus want to ask if you where able to fix the problem, thanks for any info you may give me thanks!!!
     
  9. priusgreymint

    priusgreymint Member

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    Vehicle:
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    was the problem solved?
     
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