Use hotter plugs to avoid sooting?
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This is a discussion on Use hotter plugs to avoid sooting? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I have a 2002 wrx wagon. At 30K I had to replace spark plug #2 because of misfire. At 62K ...

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    Use hotter plugs to avoid sooting?

    I have a 2002 wrx wagon.

    At 30K I had to replace spark plug #2 because of misfire. At 62K I had to replace plugs 1 and 3 again because of misfire (odb2: P0301, P0303). The plugs have carbon soot. Incredibly the two plugs failed within minutes of each other. I was able to limp home on two cylinders.

    I also tend to drive at low RPM (most of the time around 2000 RPM) and often drive short trips. I understand this contributes to the carbon sooting.

    photos of failed spark plugs

    If I rev the engine to 3000 rpm for a few seconds at the end of each short trip, would that help? According to NGK web site, hotter temperature is required to burn off the carbon soot.

    In the future, is it advisable to use a plug with hotter heat range? The OEM plug is NGK PFR6G, perhaps I should try PFR5G?

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    Moderator T0rque's Avatar
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    Use hotter plugs to avoid sooting?

    Spark plugs in a 2002 should be replaced every 30k with a fuel filter. You could use a step hotter spark plug to prevent the issue but it seems like you are getting more than 30k out of your spark plugs and you shouldn't be. Also hope you are using only premium fuel and of decent quality.


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    Why do you drive bogging the engine down?
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    Registered User Ingo's Avatar
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    Quote Originally Posted by T0rque View Post
    Spark plugs in a 2002 should be replaced every 30k with a fuel filter. You could use a step hotter spark plug to prevent the issue but it seems like you are getting more than 30k out of your spark plugs and you shouldn't be. Also hope you are using only premium fuel and of decent quality.
    Wouldn't that make the car not run at all? Sorry, couldn't resist...
    You can't have everything - where would you put it?

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    Moderator T0rque's Avatar
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    Use hotter plugs to avoid sooting?

    What?


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    Moderator Donkey's Avatar
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    I was under the impression the 02 service interval for the plugs is 60K. There should be no reason to go any hotter than stock,especially on a forced induction motor. Not to mention in this case you are just putting a band aid on the problem. If you are fouling plugs then there is an issue at hand.
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    Registered User UEDan's Avatar
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    Quote Originally Posted by T0rque View Post
    What?
    You wanna stick a fuel filter in a spark plug hole? Effin grammar nazi =P

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    Moderator T0rque's Avatar
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    Use hotter plugs to avoid sooting?

    Afaik the interval on 2.0s is 30k because they are a standard plug. The newer 2.5s and the STi is 60k


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    Moderator T0rque's Avatar
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    Use hotter plugs to avoid sooting?

    Quote Originally Posted by UEDan View Post
    You wanna stick a fuel filter in a spark plug hole? Effin grammar nazi =P
    Who in the **** would read it that way.. GTFO


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    Registered User Heide264's Avatar
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    Quote Originally Posted by T0rque View Post
    Who in the **** would read it that way.. GTFO


    I did, ha..
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    Moderator Donkey's Avatar
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    Quote Originally Posted by T0rque View Post
    Afaik the interval on 2.0s is 30k because they are a standard plug. The newer 2.5s and the STi is 60k
    Not according to the factory service manual. The 02 WRX came with platinum plugs with the change interval @ 60k while the 2.5 n/a impreza has a 30k plug change interval.
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    Moderator T0rque's Avatar
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    Use hotter plugs to avoid sooting?

    Gotcha, then donkey is right, something else is the problem fouling them that often.


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    Registered User nsibanez's Avatar
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    why would you only replace 1 or 2 spark plugs at once? just curious
    don't go too hot because you dont want to have pre ignition

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    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Quote Originally Posted by nsibanez View Post
    why would you only replace 1 or 2 spark plugs at once? just curious
    don't go too hot because you dont want to have pre ignition
    Because some people don't know about maintenance intervals, or basic car maintenance guidelines.
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    Registered User 99pgpgt's Avatar
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    Re: Use hotter plugs to avoid sooting?

    If it is stock, then run stock plugs.

    If modded, run the hottest plug you can run safely.

    People are misinformed many times on how cold or how hot to go with plugs.

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