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

shelbygirl

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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?
 

stkjock

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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
 

tjm73

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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?
 

shelbygirl

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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.
 

KRS

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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.
 

shelbygirl

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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
 

RED09GT

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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.
 

Gabe

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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.
 

KRS

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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.
 

shelbygirl

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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?
 

shelbygirl

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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.
Had that done in Jan 2019...
 

Gabe

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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?

.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
 

shelbygirl

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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.
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
 

shelbygirl

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

shelbygirl

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So, after changing the plugs, my car is not accelerating well. All I did was change the plugs, with stock plugs. The only differences are the gaps of the 100k plugs are (well worn and rounded ).059 ~ .060, and the new plugs are .044. Would you just regap the new ones to .059? Or put the old ones back in (after cleaning)?
 

RhinoRacing

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I would not put the old plugs back in. If anything re-gap the new plugs to 35-38. Make sure the coil packs are fully seated on the spark plug. If they are not they can still fire the plug so the car will run but not efficiently. I would start here and then go from there.

FYI I run a gap of 28 on my GT500 with a 2.9 Whipple and 28 in my Cobra Jet. But I run NGK plugs in both the CJ’s get changed every 10 passes as it runs on 116 octane fuel.
 
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Gabe

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So, after changing the plugs, my car is not accelerating well. All I did was change the plugs, with stock plugs. The only differences are the gaps of the 100k plugs are (well worn and rounded ).059 ~ .060, and the new plugs are .044. Would you just regap the new ones to .059? Or put the old ones back in (after cleaning)?


I would start checking the basic things. Make sure the coil packs are pushed down to make a proper contact with the plugs, make sure the coil connectors are clicked on good, and make sure the coil covers are back on and tight. The coil covers are actually what hold the coil packs onto the plugs. Without the covers, the coils will be loose and you'll most likely get misfires.
Also, if you took off the air intake, check to see if it's on tight with no leaks.
 

shelbygirl

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I would not put the old plugs back in. If anything re-gap the new plugs to 35-38. Make sure the coil packs are fully seated on the spark plug. If they are not they can still fire the plug so the car will run but not efficiently. I would start here and then go from there.
I can regap them down a bit, but how did the old plugs work so well at .060"?
 

JEWC_Motorsports

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Gap at .028 or .032, most tuners will tell you to do that and most prefer the TR6 plugs as Gabe suggested earlier.
 

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