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P0300 MAF or air filter issue?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Sanlot, Feb 20, 2012.

  1. Sanlot

    Sanlot New Member

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    ----USA----
    My CEL has come on about four times in the last month shortly after replacing the air filter with a pepboys Purolator air filter. I have cleaned the MAF sensor each time using MAF cleaner and the issue along with the CEL go away then come back in about a week.

    I dont know if the MAF sensor is bad because each time i clean it, the issue stops. also, upon first glance at the Purolator filter, i thought it looked a little thicker than the stock one but i didnt think twice about it.

    any guesses?
     
    #1 Sanlot, Feb 20, 2012
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    What happens if you clear the check engine light without taking any other action? How long does it take for P0300 to be logged again?

    DTC P0300 points to random cylinder misfiring. Here is the full list of possible suspects:

    Open or short in engine wire harness
    Connector connection
    Vacuum hose connection
    Ignition system
    Injector
    Fuel pressure
    Mass air flow meter
    Engine coolant temperature sensor
    Compression pressure
    Valve clearance
    Valve timing
    PCV hose connection
    PCV hose
    ECM
     
    #2 Patrick Wong, Feb 20, 2012
  3. Sanlot

    Sanlot New Member

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    I never actually cleared the CEL myself, but it wont go away if i dont clean the MAF sensor. every time i cleaned the MAF sensor, it clears itself. i thought it was kinda cool. i have been having this problem for a while. is it possible the air filter is too thick denying air to the intake?

    also, even though the CEL is currently on, it doent mean it is always misfiring. it misfires at random times.
     
    #3 Sanlot, Feb 20, 2012
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I would not think that a "thick" engine air filter would cause this problem since that would be no different than driving at higher altitude where the atmospheric air pressure is less. Of course, that issue would be easy to rule out by your purchase of the correct air filter from your Toyota dealer.

    Is it possible that the MAF sensor has an intermittent wiring harness connection? What would happen to the CEL if you remove and replace the wiring harness connector without cleaning the MAF sensor?
     
    #4 Patrick Wong, Feb 20, 2012
  5. Sanlot

    Sanlot New Member

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    so i let it be for about a week and the CEL light turned off. the misfiring happens a lot less but has not gone away. what does this mean?
     
    #5 Sanlot, Feb 25, 2012
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I hope that you are using MAF sensor cleaner to clean the mass air flow sensor. Do not use throttle body cleaner as that contains a lubricant which will attract dirt to the MAF sensor and cause it to perform poorly.

    I earlier provided a full list of possible problems. I suggest you will need to seek professional assistance if your MAF sensor cleaning technique is correct, and you don't see any obvious wiring harness problems.
     
    #6 Patrick Wong, Feb 25, 2012
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