Misfire problems fixed, fuel economy down

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by molgrips, Dec 21, 2015.

  1. molgrips

    molgrips Member

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    Well, it's been a long time since I came here. I used to post a lot when I first got my Prius, then I got bored, now it's started going wrong!

    A few months ago I had a problem after adding some Redex to the tank with misfiring, like a poor fuelling problem. It would come and go when driving, so I kept on driving thinking I could work whatever it was through. However it got worse, and became so bad I had to take it in. Toyota were pretty confused, but did a lot of work and determined that I had leaking injector seals and a damaged injector. This came on suddenly and immediately after I'd used the Redex, which made me suspect it.

    Anyway - now it's very smooth, no stuttering on idle (which it did from new) and super smooth ICE take-up, but there are two issues.

    1) There's a smell of petrol at the back of the car when the ICE starts from cold - this makes me worry that the cat has been damaged by the misfiring. However it did just pass its MOT which includes an emissions test.

    2) Fuel economy is down, by about 10% or so. This could be the battery - whilst trying to clear out the fuel lines by driving it, the battery did dip down to zero bars in the display for a minute or so, but I was careful not to let it happen again. Also it feels like it's more reluctant to use the battery, and starts the ICE more readily than it used to in slow driving. There's also a slightly different sound from the ICE so it might be that there's an exhaust leak somewhere. I know that exhaust leaks can cause power issues but 10%?

    Any ideas?
     
    #1 molgrips, Dec 21, 2015
  2. Munpot42

    Munpot42 Senior Member

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    I's start by checking out the 12 volt battery, but I would take it to the dealer over the gas smell......
     
    #2 Munpot42, Dec 21, 2015
  3. valde3

    valde3 Senior Member

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    Did they replace the spark plugs while diagnosing the fault?
     
    #3 valde3, Dec 21, 2015
  4. bisco

    bisco cookie crumbler

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    what kind of car are you driving, what year, and how many miles?
     
    #4 bisco, Dec 21, 2015
  5. trungdok

    trungdok Junior Member

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    Curious.. could you tell us how much did it cost to replace the injectors at the dealer? Thanks.

    As with the gas smell, could be the new injectors spray more than the computer think it should. The extra gas might not be completely burned off and thus you smell it a bit. This usually should go away as the computer readjusted itself. At least that's my guess. The poor mpg might be a result of this as well.
     
    #5 trungdok, Dec 21, 2015
  6. johnnyb588

    johnnyb588 Member

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    1. If you don't have any codes, I'd say your cat is fine. My guess for #2 would explain the gassy smell, but it's just a guess. I feel fairly confident in saying your catalytic converter is fine.

    2. My guess (again, guess) is that your A/F ratio is off. It might be that the ECU has not properly adjusted to the new equipment yet (how many miles has this been going on?). It could be as simple as unplugging the 12v for a bit and resetting the ECU. It could be much more complicated. That's where I would start. If unplugging the 12v doesn't fix it, I would talk to the dealer who performed the repair and ask for their suggestions.
     
    #6 johnnyb588, Dec 22, 2015
  7. molgrips

    molgrips Member

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    I ordered a techstream/obdII dongle from eBay but I haven't tried it out yet. Is there something I could check? Although I am familiar with VCDS for my other car I am a techstream newbie.

    I can try the unplugging of the 12v easily enough.

    Car is a 2006 mk2 with 112k miles. We bought it ex demo, 108k of those miles were done by us so we know what to expect. It is being driven mostly on the school run currently which has some tight windy lanes with lots of braking. Worst possible journey for fuel economy, but last year on the summer tyres it would do 50, now it's stickif at 45mpg. UK mpg.

    Probably done.. 500 miles since the fix, maybe. One long trip, which did better, got 57mpg when I would have expected 60.
     
    #7 molgrips, Dec 22, 2015
  8. Fingers04501

    Fingers04501 Junior Member

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    i have the exact same issue with my 2008 with 184K on it. happened for me when I replaced only one bad injector. after reconnecting the 12V battery and everything ( i always disconnect it when working around fuel) mine did the same thing. very smooth now, but runs almost constantly. having heat/ac on seems to make no difference. @trungdok, are you saying that the ECU will adjust to the new parts over time?
     
    #8 Fingers04501, Jan 19, 2016
  9. trungdok

    trungdok Junior Member

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    I would guess so. Whenever anything changed fuel / air intake ratio, I would reset the system and force it to relearn. If you already did that and it's still misbehaving after a couple hundred miles then the problem lies somewhere else.
     
    #9 trungdok, Jan 19, 2016
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