When do the spark plugs need changing?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bronze84, Jan 15, 2014.

  1. Bronze84

    Bronze84 Member

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    Hi guys.

    Am I correct in thinking that Toyota recommend changing the spark plugs at 100,000 miles on the gen II?

    The reason I ask is because on a couple of occasions the ICE ran rough for a couple of seconds when it first started up like it didn't have a spark or something on one of the plugs. Also I've noticed an slight drop in mpg, not just due to the time of year either. In winter I normally average 48-50mpg (UK) but I'm struggling to get mid 40's ATM. My pri has covered 75,000 miles so was thinking of changing them now to see if it improves?

    Cheers chaps


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  2. uart

    uart Senior Member

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    Hi Bronze. I just changed mine for the first time last week. This was at 200,000 km (125000 miles) and I was amazed how good the plugs I removed looked.

    Anyway it's a pretty easy DIY job, so if you want to replace them a bit early then go for it.
     
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  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The recommended change interval is at 120K miles. However if you notice engine misfire then it would not hurt to remove and inspect (or replace) the spark plugs now. Use only the correct NGK or Denso iridium spark plugs.

    You may find moisture in a spark plug well which would cause misfire. The spark igniter O-ring does not do a very good job of sealing the igniter opening.

    Water can drip down from the engine compartment cowl, onto the engine valve cover. If this is happening, use black sealant on the vertical seam between the two plastic cowl cover pieces.
     
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  4. Britprius

    Britprius Senior Member

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    Martin, Patrick has covered it all really, but just a couple of extra checks.
    Check the throttle body is clean.
    I have also noticed if I move the car when the engine is cold and do not allow it to warm up "not being quick enough with the EV button or forgetting it" turning it off after moving the car a few yards, next morning I can have a a short period of rough running "missfire". The gen3 Prius seems to have real problems with this, but it is a thing I notice in the gen2 to a smaller degree when it is cold. After 6 years with my car the problem "if you can call it that" has got no worse.

    John (Britprius)
     
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  5. HaroldW

    HaroldW Active Member

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    Could it be because of the variable valve timming? H
     
  6. Bronze84

    Bronze84 Member

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    Thanks for the info chaps.

    I may take them out to give them a quick health check.

    Patrick - as you mention, I too also notice water in the cup at the top of the plug
     
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