2008 Prius - revs up frequently

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by spycake, Jun 17, 2020.

  1. spycake

    spycake Junior Member

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    Hi all! My 2008 Prius has started "revving up" frequently -- every time I remove my foot from the accelerator as I prepare to brake or turn, and also occasionally just while driving around the neighborhood too. This happens regardless of hybrid battery charge level. You can hear it in the following video (around the 0:21, 0:52, and 1:07 marks) (EDIT: you may have to click the "Pop-out" icon in the upper right to stream the video, rather than download it):



    Check engine light is currently off. This started after a recent incident where the gas engine wouldn't start at all (code P3190) until I cleaned the throttle body and mass airflow sensor. A little background:
    • A couple weeks ago, I changed the oil and the cabin & engine air filters. Drove it around the block and didn't notice anything unusual, but the next time I drove it, the gas engine wouldn't turn on at all. I only got a few blocks and had to park as the car died, with the red triangle and check engine lights on the dash, plus the exclamation mark and only 1 bar on the hybrid battery on the MFD. Tried to restart, same result -- no gas engine. Checked the oil level and it was fine -- halfway between the two lines on the stick, just as I had filled it -- and the two air filters were also installed properly. Checked 12V battery via MFD and multimeter and it was normal.
    • I left it and came back the next day with a code reader, which returned P3190. So I removed the mass airflow sensor and sprayed it with cleaner, and also sprayed and wiped out the throttle body with cleaner as best as I could (had a few grimy spots and looked oily on the bottom, but didn't seem too bad -- no trouble opening it by hand). The day after that, I reinstalled the dried MAF sensor and then the gas engine turned on like normal. I idled for a minute then drove around the neighborhood while the hybrid battery recharged, before parking at home, thinking all was well. I had never cleaned those items before, so maybe they were just due.
    • But the next time I started it, I noticed the current behavior, that the car is "revving up" a lot -- every time I take my foot off the accelerator, and also at other times. The red triangle and exclamation point on the MFD both went away now that the hybrid battery has recharged, although the check engine light was still there for a couple more miles. I just cleaned the throttle body even more, and I also cleaned the hybrid battery fan in back (I had never done this before, but it only had a little light dust and dirt anyway). The revving up behavior persists, although the check engine light has gone away now too.
    Should I keep driving it like this? Anything else I should check or try? Or take it in? I just got a Carista OBD2 adapter myself, if that helps. It's only been happening for ~5 miles (I haven't taken it to the highway since all this began) but this sound seemed so unusual to me. It's high mileage (200k) but I've owned it for the last 30k+ and 4 years and haven't had any other issues. Has always been consistent 45-46 MPG. I also have a 2005 Prius, with over 240k miles, and have never noticed this behavior on that car either. (Although I've also never had the gas engine fail to start on that car!)

    *** I should also note this car was regularly parked in a detached garage with chipmunk activity a year ago, and I saw a few nut shells on the old cabin air filter. I could also hear nut shells under the hood insulation when I opened the hood, so I just cleaned that out today. I don't see any other evidence of chipmunks in or around the car.
     
  2. dolj

    dolj Senior Member

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    I suspect the car is having difficulty finding the idle throttle position (ITP) and is attempting to find it.

    Anytime you clean the MAF and/or throttle body, you should disconnect the 12 V power at the 12 V battery to reset the ECM (Engine Control Module) and, in fact, it resets all the car's ECUs. This reset forces the ECM to relearn the ITP and the fuel trims. The other ECUs will also relearn what they need to relearn. This happens after only a few drive cycles. After resetting the 12 V, you will also need to reprogram the radio stations, the driver's door window auto up/down, and the clock. You will also lose the average fuel consumption and milage on the consumption screen and the Trip A/B data. The fuel gauge will recalibrate and so will the HV battery SoC graphic (it initially resets to 60% or "6 bars") on the energy monitor screen. There may be other things as well, but these are the main ones that are noticeable.
     
    #2 dolj, Jun 18, 2020
    Last edited: Jun 18, 2020
  3. edthefox5

    edthefox5 Senior Member

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    All I hear is the valves clacking away like its low on oil or high mileage motor or poor battery power.

    Your car drives like mine lots of booming. Last time that happened to me I found out I had 3 bent rims. Never would have thought a bent rim would make the car boom like that but it does. Think I got some more bent rims. Tiny very light mag wheel very easy to bend if you hit a pot hole. My wife spends her days looking for the biggest pot holes in the county I think.

    I have cleaned my throttle body a few times over the 13 years I have owned it but never reset anything.Just get on the highway for a while.

    Usually if the engine is reving up more that's because the hybrid battery is no longer providing the power it used to even if its not throwing codes no matter if its charging or not. She just doesnt have it anymore.

    Thats stage 1 of battery failure. It will go to purple all the time like at a light or at a drive through. If your car is diving to one purple bar fast its hybrid death 1. When in that mode you must apply more engine power it happens so slow over the years you may not notice except the engine will and you will start hearing it complain with valve clakity noise. Soon you will really have to push the gas pedal down just to get going. The hybrid battery supply's the bulk of power to the car. Without a healthy hybrid battery its a really slow go kart with a tiny engine..

    G2 hybrid battery failure is the #1 post here these days.

    Oh and chipmunks check the cabin air filter behind the glove compartment there's a chipmunk Days Inn there.
     
  4. spycake

    spycake Junior Member

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    Thanks for the tip! I disconnected the 12V battery for a few minutes this morning (just pulled the white plug above it), and it indeed reset the radio, trip A/B, etc. First time I drove it, it still sounded like it did before, but the second time, that loud sound when I let up on the accelerator seemed to go away!

    So I'll consider this issue closed. Thanks again.
     
  5. spycake

    spycake Junior Member

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    Thanks for the response. I think the 12V battery reset took care of the noise that was bothering me, but there are other noises I am probably used to. :)

    I know there is a noisy wheel bearing, for one thing. Got all new tires last year and my mechanic pointed that out. Didn't say anything about rims.

    Haven't had any trouble with the hybrid battery yet -- the only time it ran down to 1 bar was when the gas engine wouldn't start.

    And yup, I replaced the cabin air filter because of the chipmunks (wasn't too bad, but there were nut shells on top). I still see them around the garage, so I am parking on the street for now. Not sure what I'll do come winter.
     
    edthefox5 likes this.
  6. sam spade 2

    sam spade 2 Senior Member

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    +1
    And just for good measure, I'd check the 12 V and it's connections again.
    Exactly what voltage were you seeing from it when you pronounced it "normal" ?

    Edit: I see the problem has been solved....for the moment.....mostly.
     
  7. dolj

    dolj Senior Member

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    Glad it solved the issue for you.

    It is moot for you now, but I'll mention it for others reading this at a later time, I should have originally mentioned that after pulling the 12 V power, you should make the car READY and let it sit with the engine running until it finishes its calibration of the idle position. Once that is done you can then take it for a test drive and the idle/off should then behave itself.
     
  8. spycake

    spycake Junior Member

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    Thanks for that, good to know too.
     
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