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P0300 code and probable misfires

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Sanlot, Jan 28, 2012.

  1. Sanlot

    Sanlot New Member

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    2007 Prius
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    ----USA----
    Recently i started the car and it was shaking more that usual. the CEL light came stating P0300 with random misfires. It sounds and feels like misfires so i believe this is true.

    I cleaned the MAF sensor with carb cleaner and the CEL turned off, however, the problem persists. I have not had the fuel pressure checked because it can be expensive with no guarantee. I plan on calling the dealer to see if it is in warranty. Any suggestions?

    The car is a 2007 with about 40K miles logged. I recently changed the oil and air filter if that matters.

    Thanks!
     
    #1 Sanlot, Jan 28, 2012
  2. seilerts

    seilerts Battery Curmudgeon

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    You used carb cleaner on the MAF? Rather than MAF sensor cleaner? MAFs don't like carb cleaner.

    How many quarts of oil did you add? How high is the level on the dipstick?
     
    #2 seilerts, Jan 28, 2012
    1 person likes this.
  3. V8Cobrakid

    V8Cobrakid Green Handyman

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    i used to get weird vsc messages in hard turns (voltage drop in sensors) and misfires when my 12v was dying. it then turned into a failing ignition coil (toppers to the spark plugs) that cost me about 80 bucks. i had a cylinder no longer firing. the car didn't pick it up but it was obvious to me... reduced power and mpg.. higher revs.. etc... the only way i was able to found out for sure was by listening carefully then pulling the coils out 1 by 1... you can't un-clip them (brown clip?) and you can't pull more than two or else the car will turn off. only pull strait up (after removing the bolts that hold them down)

    but... i think your problem is probably more 12v than coils... unless you replaced the 12v recently... in that case it would possibly be one of your coils (possibly)
     
    #3 V8Cobrakid, Jan 28, 2012
  4. Sanlot

    Sanlot New Member

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    I added 3.5 quarts of 5W-30 with no pre-filling the filter. yesterday, i opened my throttle body and noticed a little oil so i took out about .5 quarts but it did not fix the problem.
     
    #4 Sanlot, Jan 28, 2012
  5. Sanlot

    Sanlot New Member

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    I replace my 12v battery about 3 months ago with a optima yellow top.
     
    #5 Sanlot, Jan 28, 2012
  6. bisco

    bisco cookie crumbler

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    where is the level on the dipstick?
     
    #6 bisco, Jan 28, 2012
  7. Sanlot

    Sanlot New Member

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    right at half way after i removed 0.5 quarts.
     
    #7 Sanlot, Jan 28, 2012
  8. Sanlot

    Sanlot New Member

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    For future users,

    i think i figured it out. I used a Carb and air cleaner to spray the throttle body. there was a small amount of build up around the rim of the throttle body plate which i believe was allowing a small amount of air to leak into the engine. i have driven my car numerous time since and it seems to work fine.
     
    #8 Sanlot, Jan 28, 2012
  9. orange4boy

    orange4boy Member

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    Just had the same symptoms and codes. Ramdom misfire P0300, and P0302, P0303, P0304. Mine turned out to be a dead ignitor. Lifting the ignitors over an inch out of their sockets with the engine running revealed a silent ignitor between it's cracking bretheren.
     
    #9 orange4boy, Feb 21, 2012
    1 person likes this.
  10. Sanlot

    Sanlot New Member

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    Well, i am still having that problem but i am going to check out my coil asap. i will post the results. THANKS!!!!
     
    #10 Sanlot, Mar 15, 2012
  11. Sanlot

    Sanlot New Member

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    When i lifted the coils (one at a time), all four would ping or crackle for a second then stop and the engine appeared to run smooth. when placing them back in, it would crackle again. Basically, they all sounded the exact same as i removed them.

    Does that mean they are all good?
     
    #11 Sanlot, Mar 15, 2012
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