Spark Plugs

Discussion in '2004 - 2008 Ford F150 Truck Forum' started by 57FordGuy, Aug 19, 2015.

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  1. 57FordGuy Founding Member

    I've used dielectric grease before. After watching the video I see I've used it wrong. I have put it on the terminals and in the distributor cap/coil pack. And I've always changed plugwires with plugs. Do I need new boots?
     
    Last edited: Aug 25, 2015
    57FordGuy, Aug 25, 2015
    #16

  2. 57FordGuy Founding Member

    Something has changed yet again. I'm seeing the Motorcraft plug number is SP 546. This is superseding SP 515. And I'm finding an Autolite HT 15 plug. I don't think Ford owns either one of these brands any more. So far I've only seen the SP 546 for sell on Amazon. And the Autolite is much cheaper than most, which usually equals not as good as most.

    And no in these 2 years I haven't changed my plugs. No problems have showed until lately. Most of the time my truck runs great. But at times now it stutters if I try to ease it from say 50 MPH to 60 without using enough petal to downshift. Almost feels like some transmission trouble, but so far all the information I'm finding online says this is due to the plugs wearing out. No CEL yet. But I've got to change the plugs while the weather is best!
     
    57FordGuy, Oct 20, 2017
    #17

  3. FTZ HAIC Staff Member Oregon Chapter Founding Member

    Sorry I didn't notice until now that you asked a question in this thread a couple of years ago!

    The misfire could also be due to a back COP. Any water intrusion into them can cause it. Due to the way the cylinder head is shaped, it can sometimes take weeks after water gets in before it affects the COP. Basically, since the head has a tube the plug resides in, if water makes its way down there it can sit for a while. As it steams, the steam can make its way up into the boot then into the coil. Then when the conditions are right, like a cold day, the water condenses in the plug. That's the main reason for the grease, to prevent any moisture from getting in the coil (plus it helps make removing the boot from the plug much easier).

    The SP546 has a longer smooth part below the threads, and the groove at the top of the smooth part is now gone (probably for a better combustion seal). I wouldn't be surprised if they also strengthened the weld between the top and bottom pieces as well, to further help prevent breakage when removing them.
     
    FTZ HAIC, Oct 20, 2017
    #18
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