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Discussion Starter · #1 ·
About this time last summer after gettin my 3.90 i burned up 2 coils,,,,, now im runnin a procharger too and just the other night, stepped on it and got that same feeling... i think i might have burned up a couple more....... I just have the stock ones on now, but figure since im running heavier injectors maybe i need more spark.... I also have new plugs in it too.. What should I switch to if it is the coils? What else could it be if not the coils, It was maybe 20 degrees colder outside than my car was tuned at, could that have caused it to stumble?
 

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that is what happened with mine when i first went to get it dynoed. the extra pressure was blowing out one of my sparks and i was getting missfires. no code was being thrown so i had no idea what coil pack it was. i bought a whole new set from summitt ($270 if i remember) and that solved the problem.
 

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OK, replace the whole set with OE parts (the aftermarket items cost more and are potential trouble). Its highly unlikely that you will need more spark than the Ford parts can supply.

What IS likely is that you need cooler plugs (at least 1 heat range, and I would try them at 2 ranges cooler if you are running hard or mainly at the track). If you are generating more than 9 pounds of boost, you might also go with a shorter gap (.32 if I recall) if you get spark blow-out.

If the cooler range copper core Motorcraft plugs don't work for you, you might need to go with an NGK plug.
 

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Discussion Starter · #4 ·
OK, replace the whole set with OE parts (the aftermarket items cost more and are potential trouble).

What kind of potential trouble? How can i tell if my coil is bad when i pull them? I had a shop do it last time, but i believe my coils are under my valve covers on the 99. These are brand new plugs also... installed to match up with the procharger..
 

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Coils

What kind of potential trouble? How can i tell if my coil is bad when i pull them? I had a shop do it last time, but i believe my coils are under my valve covers on the 99. These are brand new plugs also... installed to match up with the procharger..
A set of coils SHOULD last a long time. On the 99-04 cars, they are COPs (coils on plugs). Earlier model 4.6s used coil packs. If you have a dohc engine, they are in the valve covers. A sohc engine is different.

Aftermarket COPs have been implicated in many problems, usually of the "it can't be the COPs causing the misfire, they are brand new" variety. You should be getting one of the OBDII trouble codes regarding bad coils if they are the source of the problem.
 

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Correct don't believe the hype with those aftermarket COP's, stick with OEM Ford, this has been debated in SVT Forums and plenty of guys with 800+ HP Cobras still use them!
 

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i have nothing against ford or oem products but dont go to a dealer. when i was replacing my COPs i went to ford and they were trying to charge $110 per coil! look around online, there are some sites that sell oem ford coil packs for like $30-40 each.
 

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Discussion Starter · #9 ·
alright thanks! good to know i wont need anything over expensive. I shouldn't need my car retuned when i replace the coils should i?
 

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Nope no need for a tune and TripleBlack mentioned a few good points, I'd run the NGK Iridium 7IX plugs (2 heat ranges cooler) gapped to .032 or for a few bucks cheaper their Tr-6 copper which is 1 heat range cooler than stock!
Got a new set of Motorcraft OEM COPS when I rebuilt my motor on Ebay for $25 each, $200 a set!
 

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PM me if you still need some COPS, I called my friend and can hook you up with a set from a low mile (under 10K) 99 Cobra that got wrecked!
 

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Discussion Starter · #12 ·
i need to check the ses light to see which coil it is,,,,, but if i replace one coil with a different brand, do i need to replace all of them?
 

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Once they start to go, they ALL start to go. Oh, they might wait a week or two between failure, and give you all sorts of fun intermitent crap to puzzle over along the way...

And the aftermarket items are often troublesome.
 
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