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Discussion Starter #1
2004 2.3L Duratec, I need to replace a coil, I don't want to pay the price from the dealership so I was looking on Rockauto and Amazon. I was thinking I should get the Motorcraft Part #DG541.

I'm not looking for a performance coil, just a reliable replacement. What have you guys used for these engine that works well?

I also found the Denso Coil part # 6736010 This looks like a good choice too but I am not sure.
 

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Vince your Moderator
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He is a good guy
 

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(Shaking my head)...................for one damn coil......................sheeeesh.
 

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C2H5OH
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(Shaking my head)...................for one damn coil......................sheeeesh.

and it's just going to go bad again because most are just part replacers.
Those how address the why's are the ones who fix the problems.
 

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Too cynical once in a while Bud, I've yet to diagnose "why" a coil went bad on mine but I did spend quite a while diagnosing that as a problem.

Didn't ask the OP what diagnosis he did, left it at answering the question this time.
 

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Discussion Starter #8
Well my Diagnosis was done with pretty much the best way you can do it and it was suggested by Sailor who has been very helpful. Here is how I did it.

Read codes, found a 301 code. Replaced all plugs and moved the suspect coil to number 4 cylinder. Drove a week. Checked codes, found a 304 code. Looks like #4 coil is the offender but hey, could be a bad new plug, it has happened before. I'm betting it's the coil though.

I decided on the Denso Coil and bought it from Amazon because it was a good price and I have had good luck with Denso products in the past and the do make a lot of OEM parts for different companies.

As for it just happening again, are you saying that there is something causing the coils to go bad? I'm pretty new to the Ford Focus scene so please give me details because other than a crappy MSD box causing a repeated coil failure I have never seen a stock electronic ignition cause a new coil to just fail.

I had a coil pack on my Cadillac northstar V8 go bad, (the set up against the firewall) and replaced it 3 years ago and it's been great sense then.
 

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C2H5OH
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A coil does not care what car it's on. All of them work in similar fashion.


The major determining factor is the spark plug gap.
It takes a certain amount of Voltage/Amperage to jump a gap. The larger the gap, to more Voltage/Amperage required.

Higher Voltage/Amperage requirements cause more heat, both across the gap and inside the coil. It's the inside the coil we're concerned about because this is predominately why a coil will go bad.

In a nutshell, a coil goes bad because the spark plugs have not been checked/changed at the correct time.
It's a case where preventative maintenance will save money.
 

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Discussion Starter #10
A coil does not care what car it's on. All of them work in similar fashion.


The major determining factor is the spark plug gap.
It takes a certain amount of Voltage/Amperage to jump a gap. The larger the gap, to more Voltage/Amperage required.

Higher Voltage/Amperage requirements cause more heat, both across the gap and inside the coil. It's the inside the coil we're concerned about because this is predominately why a coil will go bad.

In a nutshell, a coil goes bad because the spark plugs have not been checked/changed at the correct time.
It's a case where preventative maintenance will save money.
I might be new on this forum and the ford focus but I'm not new to building high horse motors, racing and performance setups in general. If you think the only reason a coil is going to fail is because of spark plug gap then you need to re-think your line of reasoning. HEAT, VIBRATION, and Moisture are going to kill a modern coil long before a spark plug gap than is .002 over manufacturers specs will.
 

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C2H5OH
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Modern cars aren't the old oil cooled coils you're used to. They are solid state, vibration doesn't affect them, and the heat concern is internal not external.
 

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Discussion Starter #12
Modern cars aren't the old oil cooled coils you're used to. They are solid state, vibration doesn't affect them, and the heat concern is internal not external.
Are you kidding me? All it takes if for the epoxy sealant inside a new modern coil or PCM or whatever to crack or come apart even the slightest amount and it's all over for that coil or part. I guess you live in a world where there are never any failures of a manufactures components due to bad assembly or a simple breakdown in the manufacturing process.

After your last post I am going to have to say there is no point in arguing with you because you must be the resident troll.
 

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Ignition components are legitimate wear items. It's a known and proven fact that little bits of electrode material get transported with every spark event, and ignition coils/packs will ramp up the initial spark firing process using more and more voltage to overcome any resistance encountered during the combustion event. An ignition coil will literally kill itself to keep an engine running.

Iminhell, you're clearly a smart guy but don't assume everyone else is a stupid lost cause just for asking questions here. Or for answering them, even somewhat incorrectly.

I see you're on that same path of reasoning but come on man.
 

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I'm blaming nothing but time.

Mileage below plug replacement interval (even if I don't like the 100k official), gap not measurably increased, and by now all four coils had barely visible surface cracking of the epoxy.

Sometimes parts just don't make their expected lifespan, or may age out before expected mileage is reached.

Replacement plugs made no difference, the bad coil continued to deteriorate until it was readily traceable to one specific problem coil.

Notably the OP's car is of the same model year/engine type so this may not be all that uncommon as time goes on.
 
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