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Denso OEM from Dealer - Leave Pre-gapped or not ?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sas0611, Jul 11, 2017.

  1. sas0611

    sas0611 Member

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    Hi I'm going to do my Spark Plugs this weekend. Old ones have 135k on them.I bought a set of Denso iridium plugs from the dealer. The 4 cost me 41.00 which I didn't think was bad considering they are Toyota parts. They come pre-gapped at .044. This is larger gap than specified for the prius. So should I go ahead and close the gap down. I can gap them down to .040 inches or 1.0160 mm. This would be in the lower range of toyota's recommended gap. Would this be better than leaving in out of range setting of .044 as it comes from factory ?

    Also, I'm feeling a little anxious about encountering a seized situation upon pulling old plugs after reading some accounts of difficult to remove plugs post by others. How often does this actually happen. I'm sure I'm not hearing about the changes people are doing without incidents which are probably lot more common than the horror stories I've read.
     
    #1 sas0611, Jul 11, 2017
  2. ChapmanF

    ChapmanF Senior Member

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    Given that the pre-gap you report is within 0.001" of the spec in the 2008 owner's manual, it is probably just as well to leave the gap alone as the manual suggests. As I understand it, the iridium electrode may not take well to gap adjustment in the field.

    -Chap

    gap.png
     
    #2 ChapmanF, Jul 11, 2017
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Personally, I will gap the plugs to 1 mm as that is on the low end of the spec which is a range of 1.0 to 1.1 mm. The plugs are supposed to be replaced at a gap of 1.2 mm or when 120K miles have been logged.

    If you find the plugs are binding as you remove them, it may help to exert slow and steady effort to loosen them.
     
    #3 Patrick Wong, Jul 11, 2017
  4. sas0611

    sas0611 Member

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    Makes sense knowing that gap will naturally increase over time to start at lower end of recommendation than to start at value that is already outside the upper limits. I think that the warning about adjusting gaps on these iridium plugs apply to doing so after the plugs have seen active duty and not necessarily relevant to initial setup. Also, I think that they see a lot of people damaging the center wire because the installer is not paying attention and/or are using the wrong type of gap tool to bend them.

    Would it be a mistake to use the 'tap the outer electrode lightly on a hard table method' so as to get the gap closed nearer to lower limit ? It probably would be a more controlled means of making small changes I'm thinking ?
     
    #4 sas0611, Jul 11, 2017
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I use a gap tool that grabs the ground electrode and allows you to move it closer or farther from the center electrode. Buy at any auto parts store. I agree that the caution about adjusting iridium plugs applies to used plugs.
     
    #5 Patrick Wong, Jul 11, 2017
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I don't think iridium plug gaps change much, if at all. And as chap says, manufacturers often caution to not adjust. Think they're fine.
     
    #6 Mendel Leisk, Jul 12, 2017
  7. wjtracy

    wjtracy Senior Member

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    Patrick is the expert but I did not change the gap. Don't forget the Iridium is not going change much...you will see this on the plugs you take out.

    I did mine at 135K and they fought me the whole way like I was reeling in a 20-lb cat fish.
    But it was soft gunk they just moved slowly, without a clear feeling of freeness once loose.
    It felt funny ...I kept checking to see if I broke my ratchet wrench or the plug, but all OK. Just go slow and get the hang of it.
     
    #7 wjtracy, Jul 12, 2017
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