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Good COP Replacement?

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Old 04-15-2011, 07:55 PM
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MustangGt40th
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Default Good COP Replacement?

My car when cold has an audible misfire when idling, and I have a gotten a few codes for random misfire. I just replaced the plugs last summer so I guess now it's time to do the COP's.

I've been searching for days on a good replacement COP set. I have read mostly that Motorcraft is the way to go, but I'm not exactly willing/able to spend $80+ for each one. I have read hit and miss stuff on the Accel ones that are sold on American Muscle. And heard pretty much all bad on Granetelli stuff. I'm not wanting extra spark to get more hp. I just want a good set of COP's that are cheaper than the OEM ones, but at the same time, comparable to the longevity of them. Right now I am leaning towards the Accel ones since they are the cheapest ones I have found that are from a reputable company. Any help to get me pointed in the right direction would be greatly appreciated!
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Old 04-15-2011, 08:16 PM
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zero2005
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from what i've read most COPs all have the same manufacturer, just different brand names and minor tweaks. i think the only one that is completely redesigned is the Weapon-X COP.

i'd say before dumping money into replacing parts, especially since cops arent known for randomly dieing, try and diagnose whats happening first. provide the codes that you've been getting, and maybe make a video. what plugs did you replace them with? what was the gap?

edit: just remembered, you should be able to check cops with a multimeter, i cant remember what its supposed to read, but i'm sure if you did a search you'd find something.
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Old 04-15-2011, 08:46 PM
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Well if it makes a difference the car has 82,xxx miles on it.
And i replaces plugs with these:
http://www.americanmuscle.com/ngk-sparkplugs-3403.html

I gapped them 0.054.

I don't have access to a multimeter, but I do have some experience using them in school.

And it was one of the codes for Random Intermittent Misfire. When the light flashes again I'll read the code with my tuner. My car just doesnt seem to run as smooth as it once did along with the occasional random misfires. Just thought replacing the COP's would be a good place to start, and from what I've read they are like popcorn, once one pops the rest are soon to follow; so I was planning to just replace them all.
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Old 04-15-2011, 08:49 PM
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DreamerGT
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If your looking for a good set of cop's go OEM motorcraft $45 each a rockauto.com
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Old 04-15-2011, 08:52 PM
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Originally Posted by DreamerGT View Post
If your looking for a good set of cop's go OEM motorcraft $45 each a rockauto.com
How are they so much cheaper on this website than everywhere else I've looked?? That is closer to the price range I was thinking they should be.
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Old 04-15-2011, 09:50 PM
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cuz rockauto is awesome. i bought a **** ton of gaskets from them when i reassembled my motor, quick shipping.

i would definately look into finding out what is causing it rather than just toss parts at it. hell, it could just be a loose or corroded wire. and you dont know which cop it is, so either you have to buy all 8, or buy 1 or 2 and swap them out to see if you can isolate the bad one(s). i dunno bout you, but i wouldnt wanna spend 360 bucks on cops unless i had to.

i'm assuming you have a diablo tuner from your signature, are you sure its not something with the tune?

if you really think it's the cops' maybe find someone else with stang, or any 4.6 with cops and see if you could "borrow" them and run your car with those known good ones...
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Old 04-15-2011, 11:54 PM
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Z28KLR
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If it's one or more of the cop's, the misfire code you're getting should call out specifically which cylinders are having a problem. At least that's my experience with it.
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Old 04-16-2011, 08:27 AM
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The first thing to do is to pull the COPs and inspect the boots for signs of arcing or deterioration (dis-colourisation or a burnt smell). You can buy new boots and springs at most FLAPS, or online here.

Normally the COP only uses a small fraction of it's potential power to fire the plug. However once the COP starts dumping more of it's charge through the boot the situation worsens as the resistance of that path lessens over time--and the COP dumps more and more of it's potential. This causes the COP to over heat and eventually burn out.

Using my DIY COP tester (aka COP Destroyer) I have found I can burnout a COP with 20-30 rapid succession full dumps across a 20mm gap. The COP will reach 250F on the outside.

A bit less stressful test will weaken one to the point that it can only barely fire across the stock 0.054" gap.

This is from the older post, yet it is relevant to the OPs question, here are what I found testing four Accel COPs vs. four Motorcraft units:



You can see that the Ford units consistently delivered 5kV more than the Accel devices. The Accel COPs have about 20k miles on them, they were four of the five that lasted that long. The other 3 died one after the other over a two week period between 19k and 20k miles; one completely dead the other two became too weak to fire the plug at higher loads.

The Ford COPs had about 70k on them at that point, they now have 85k on 'em and are working fine.

Check out the COP how-to sticky for more about COPs including how to quick-test them with a multimeter...
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Old 04-16-2011, 09:39 AM
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Thanks guys for the help! When I get the code again I'll see which cylinder(s) it is that is misfiring. I will also pull out the COP's and check for any deterioration. My buddy has a 02 Saleen that has basically new ones so I will take a few of his off and put them in mine to see if it makes a difference.
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Old 04-16-2011, 10:57 AM
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Stock Ebay lifetime warrantied for $120. Anything else is stupid for a car under 7k rpm. I haven't seen a set of COP that increased spark and didn't decrease life and reliability.
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