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random conversation - P0171

Discussion in 'Generation 1 Prius Discussion' started by ronlewis, May 22, 2024.

  1. ronlewis

    ronlewis Active Member

    Joined:
    Dec 5, 2016
    938
    188
    1
    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    Car set this code, so I used some MAF spray. Right after that, it showed P0300, 01, and 04 codes, but I cleared them all and none have come back. I think the misfires could have been overspray? I drenched it good.

    Regardless, I still hear a misfire/feel a shudder. Very rhythmic. Idles smooth for ~10 seconds, then a slight miss for ~5 seconds. Was doing that over and over, with/without AC.

    The next part to check/replace in the diagnosis process is the OX1 sensor, then injectors. And, I don't mind doing that. I have spares, Just wondering if anything else lines up better as the cause of that rhythmic shudder. The car runs/drives fine otherwise, although I expect the codes will reappear soon.
     
    #1 ronlewis, May 22, 2024
  2. Josey

    Josey Active Member

    Joined:
    Jun 10, 2019
    290
    111
    0
    Location:
    Virginia
    Vehicle:
    2003 Prius
    Model:
    One
    Especially with the P0171, it sounds like you might have a vacuum leak someplace. They commonly do present as somewhat rhythmic rising/falling idle. And will pop the 0171
     
    #2 Josey, May 29, 2024
    ronlewis likes this.
  3. ronlewis

    ronlewis Active Member

    Joined:
    Dec 5, 2016
    938
    188
    1
    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    Thanks, Josey. This car had an aftermarket cat when I bought it, but the vacuum canister hadn't been hacked so it showed a CEL. I added the vacuum canister back, but maybe it's leaking. I've driven the car ~30m since I cleared the codes and they still haven't come back, but I still feel the miss at idle, just barely. I'm going to drive it again today and see how it does.
     
    #3 ronlewis, May 30, 2024
  4. mroberds

    mroberds Member

    Joined:
    Nov 6, 2010
    133
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    Location:
    .
    Vehicle:
    2001 Prius
    Model:
    N/A
    I got one of the "fuel trim" codes on my '01 - I think it was the "I'm making it rich as hell but I still can't satisfy the O2 sensor", but I'm not 100% sure on that.

    I cleaned the MAF, like you did.

    I also checked the vacuum? hoses coming from the front (FRONT) of the throttle body. The one on the driver's side (IIRC) goes straight up from the throttle body for a couple of inches, and then turns to run mostly-horizontally across the top of the engine, towards the back of the head. It has a sponge-rubber sleeve on it for much of its length, as protection. I pushed the sleeve up from the throttle body (it's like pushing a sock down your leg) and found a little crack in the rubber hose, right where the molded-in turn is.

    My high-tech fix was to wrap several turns of fresh electrical tape around the hose, over the crack, clear codes, and motor down the road. So far, the code has stayed gone. :)
     
    #4 mroberds, Jul 29, 2024
    ronlewis and Josey like this.
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