2008 Prius Engine Running Rough - Tried common solutions

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by hoosierprius81, Jun 24, 2021.

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  1. hoosierprius81

    hoosierprius81 Junior Member

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    Greetings Friends,

    I have a 2008 Prius with approx. 180k miles. Not too long ago the gas engine started running rough. I changed the oil because it was due for a change and was a little low. This did not improve the situation.

    I hopped on here and found some post.

    The air filter is brand new
    The throttle bottle is clean (not stuck or anything)
    The MAF sensor is clean as well
    Spark plugs were replaced with new NKG at approx. 160k miles

    I put it in maintenance mode so the engine would run and unplugged each coil pack one at a time. So I know its not the coil packs because each time I unplugged one, it ran worse and wanted to stall.

    I disconnected the 12V battery to "reset" the computer and that didn't help.

    Only CEL are for a bad catalytic convertor (don't think thats related to this since its been on since I bought it and this just started a few weeks ago)

    Below are two videos for reference:

    This video is just the engine running (sorry its sideways but should still be able to hear it)


    This video shows the engine running and being put under load


    Not sure what is wrong with it and not sure where to go next.
    Hopping the gas engine isn't on its way out.

    Thanks in advance for any help.
     
    #1 hoosierprius81, Jun 24, 2021
  2. JC91006

    JC91006 Senior Member

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    When you say the oil was a "little low". How low was it? And how many times do you let it get low? Burning a lot of oil can be a sign the engine will soon need to be replaced.

    Oil is the blood of the engine, without the proper oil levels (and clean oil), the engine would slowly die.
     
    #2 JC91006, Jun 24, 2021
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  3. hoosierprius81

    hoosierprius81 Junior Member

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    It was just a tick above the "MIN" line of the dipstick. I am good about checking the oil and this is the first time since I have owned it that it has gotten that low.
     
    #3 hoosierprius81, Jun 24, 2021
  4. JC91006

    JC91006 Senior Member

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    Does the car run good and give good gas mileage? It just sounds rough to you?

    The sound in the engine might be coming from the water pump and pulley
     
    #4 JC91006, Jun 24, 2021
  5. hoosierprius81

    hoosierprius81 Junior Member

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    Seems to drive and run just fine. Gas mileage is good for 180k (AVG 35-40 depending on city or highway). I think it sounds rough. Were you able to hear it in the videos?

    I had not considered it being the water pump and pulley. Is there a way to do a better diagnosis on them?
     
    #5 hoosierprius81, Jun 24, 2021
  6. JC91006

    JC91006 Senior Member

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    I did listen and watch the video. The water pump is attached to the belt on the passenger side of the engine. You can try and see if the noise is louder on that side of the engine vs the driver's side. If they are pretty much the same on both sides, then the noise might be from the engine.

    35-40mpg is pretty low for this car. So the performance might be suffering from a worn engine. But luck would have it, these engines are cheap so if everything else is in good shape, then you can replace the engine when it fails
     
    #6 JC91006, Jun 24, 2021
  7. SFO

    SFO Senior Member

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    How much oil does it generally consume over what oil change interval, and do you use synthetic?

    You mentioned replacing the plugs with new NGKs, which part # and where did you source them from?

    Do you generally use quality "top tier gas" that contains additional detergents?

    Have you tried using PEA additives in the gas tank? (Tecron, BG products, Regain, Redline, etc)

    Do you possess an OBD2 code reader, or a Mini-VCI cable and techstream installed on a windows device?
     
    #7 SFO, Jun 25, 2021
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  8. TMR-JWAP

    TMR-JWAP Senior Member

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    Try replacing the NGK's with Denso 3324 (SK16R11) . The 1.5 can be finicky sometimes. Try not to buy counterfeits........

    Swap the catalytic converter out. Buy an inexpensive front half assembly that includes both cats. Cut your old exhaust a couple inches in front of the resonator and install the replacement. Sell the OEM cat to recoup your money plus some. (actually a lot of 'some')

    An engine has to breathe, get fuel and fire (with correct timing of those events) to run correctly.

    If you're confident of the breathing and the fire, it only leaves fuel and timing..
     
    #8 TMR-JWAP, Jun 25, 2021
  9. edthefox5

    edthefox5 Senior Member

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    Your engine is eating oil cat probably damaged.

    Engine sounds bad though. Try the old long screwdriver to the ear listen trick and localize where all that noise is coming from if not the water pump.
    Sounds like under the valve cover chain noise. Motor sounds whooped.

    at that mileage if I was in replacing the plugs I would have pulled the valve cover off too and look in there check the chain. It’s very easy to pull the valve cover off.

    listen to the valve cover and then listen to the oil pan.

    what kind of oil do you use?
     
    #9 edthefox5, Jun 25, 2021
  10. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    No, no, no. Your catalytic converter is probably fine as a clogged converter causing a problem at idle won't let you get up to speed on the highway.

    My 2005 Prius came with NGK plugs from the factory, and it's not the only one. I'd imagine your CEL would be on if you has a spark plug problem.

    Maybe take the belt off and run the engine for only a minute and see if the noise goes away?

    Posted via the PriusChat mobile app.
     
    #10 Avi's Advanced Automotive, Jun 27, 2021
  11. dolj

    dolj Senior Member

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    The NGK plug is IFR5A11. Toyota recommends either the Denso or NGK.
     
    #11 dolj, Jun 28, 2021
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