07 GT500 coil packs with 105k miles: Test? Replace? Leave 'em?

Discussion in '2007+ Mustang GT500 Tech' started by shelbygirl, Jul 1, 2020.

  1. shelbygirl

    shelbygirl Junior Member

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    With 105k miles, can the coil packs be tested to see if they are still within spec?

    Should I just fork out $240 for the Ford Performance set?

    Change out plugs for a "colder" set, since there are 100k miles?

    Copper, Iridium, Platinum.?

    My guess is just replace the coil packs and use Ford Performance oem platinum plugs.

    What did you do, and are you happy with the money spent?
     
  2. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

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    if the car is basically stock, no need to replace the coils, yes to the plugs, no to the colder set as well if the car is stock.

    Iridium or platinum are fine - stock spec
     
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  3. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

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    If you have no fault codes and no issues with ignition, just change the plugs. No need to touch the coils.

    My F150 had a code for spark issue recently. Checking the code revealed it is was cylinder #1. Changed that coil. All is good. The truck is 13 years old. I had to change #7 coil 2 or 3 years ago. Same thing. Threw a code. The other 6 are OEM coils that left he dealer's lot on day 1. Truck has 136,000 miles. Don't fall into the money wasting trap of changing all or any of them unless they need it. Some people say if one's bad change them all. One may go bad and the rest could be fine for a decade.

    I suppose if you want to piss money away you can. By why do that?
     
  4. shelbygirl

    shelbygirl Junior Member

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    I took one out to look at it today. The electrode was rounded, and there was some sort of splatter on the curved metal piece that forms the gap. When I look at new ones, the electrodes are cylindrical and flat. I plan on keeping the car forever, so $40 for new ones is ok. Although Iridium is tempting, but may just be a gimmick. My last snowmobile ran better with Iridium for sure.
     
  5. KRS

    KRS Junior Member

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    Can you post pictures of the spatter on the ground electrode and is the spatter on all of them?

    I’d suggest stock replacements. Check the gap, and I always put a “very small” amount of never-seize on the plug threads.
     
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  6. shelbygirl

    shelbygirl Junior Member

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    Ok, this has turned into some spectacle. I can't get a straight answer from 3 different Ford Dealerships here in Washington. The parts department says the gap is not listed in their computer system. The service advisors did not know either. One referred me to their technician. He says .033" ~ .037":
    All did say that the Ford Motorcraft Platinum are recommended and listed as SP-405.
    When I checked with Autozone and Baxter Auto Parts, their systems show .044"
    I had them pull 2 separate manufacturers sets, 1 from Bosch and Autolite...their gaps are .044"
    So, another technician says to look under the hood at the emission specs.
    Here is the actual sticker... it says, "See Spec Book", so I go to my spec book...it says AGSF-22FM1, which are the ones that I have. (see actual box spec). When I go to the Spec page 246 in the actual owners manual, it says see paragraph 2: "For spark plug replacement, see your authorized dealer.
    I already put in the Motorcraft SP-405 @ .044" gap. Seems fine.
    Should I take them out and re-gap to .037"? I have read that you should never re-gap thin wire platinum, because it is brittle. I am at a loss...
    You can see my original plugs, both the electrode (rounded off), and the inner smoothed contact area. (In my opinion, should have a platinum disc on that area) gt500 emissions 1.jpg gt500 motocraft info.jpg gt500 plug electrode 100k.jpg gt500 plug fire dia.jpg gt500 spark para 2.jpg gt500 spark para 2.jpg gt500 spark spec.jpg
     
  7. RED09GT

    RED09GT Senior Member S197 Team Member

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    0.044" is stock but is on the high side for a boosted motor.
    If you are running it hard or taking it to the track, or adding more boost, I'd try 0.035" but if you are just wringing it out on the street from time to time and are at stock boost levels, 0.044" is just fine.
     
  8. Gabe

    Gabe Whippled Coyote

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    Get some NGK TR6 plugs, gap them to .032-.033 and call it a day.
    Less than an hour to install.

    They're not platinum so they need to be changed every 20k but they are an awesome plug for the Cobra 4.6 and the Shelby 5.4 engines.
     
  9. KRS

    KRS Junior Member

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    Stock plugs and stock gap and you’re set! I believe .044 is the correct gap.

    A couple of other things you may wish to consider would be a coolant change and a Trans fluid change. The coolant change is to refresh the corrosion inhibitors, go with OEM coolant 50/50 mix with deionized water. Trans fluid will give you smoother shifting if you go with Mobil 1, and it’s Tremec recommended.
     
  10. shelbygirl

    shelbygirl Junior Member

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    So, I did install the stock Motorcraft .044" SP-405 Platinum plugs. Left the battery disconnected for 4 hours after that. I am not very happy with the performance now. I drove 150 miles today, hoping the computer and sensors would "adjust". I measured the plugs that I took out and they are all .059" to .060". How in the hell did my car perform so well before?
    No codes ever. I was not having any problems, other than just the higher mileage. I got an actual printout from a dealership, that shows in the ford tech services site - only available for dealerships and techs.
    It states that the gap should be .033" to .037", yet the stock plug and the ONLY one listed in any manual, says it is SP-405 and gapped .041" to .047" (but always go to nominal .044"). Since these are .044", I wonder if I should just close the gap down to .033" and see what happens. Or get a double platinum @ .055". Or, just clean the plugs I took out, and put them back in?
     
  11. shelbygirl

    shelbygirl Junior Member

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    Had that done in Jan 2019...
     
  12. Gabe

    Gabe Whippled Coyote

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    .044 is huge, but what do I know, I've only been working on my wife's 656 rwhp GT500 for 5-6 years now.
    I mentioned the NGK TR6 plugs above, it would've been about $20.
    My wife's car runs awesome on them.
    I run a .028 gap in her car because of the higher boost, she's at 18 psi
    On a stock setup, .033-.034 should be good
     
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  13. shelbygirl

    shelbygirl Junior Member

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    The stock plugs have blue painted rings on the ceramic ribs, the new plugs I got do not have the blue rings. Why is that? gt500 plug blue and white.jpg
     
  14. jewc75

    jewc75 forum member

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    Looking at that plug you need to run a better quality fuel.
     
  15. shelbygirl

    shelbygirl Junior Member

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    The plugs have 105000 miles (20k were in Europe) But, always 92 or higher octane. Here in the Pacific Northwest, most gas has 10% ethanol. If I had the money, I would do 4 separate dyno tests, 1 with ethanol and platinum, 1 with ethanol and iridium, 1 with non-ethanol and platinum, and 1 non-ethanol and iridium.
     
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