New spark plugs, occasional misfire

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But only jumping 25 thousandths gap. Not a lot of voltage.
Could just be one plug has suboptimal indexing.

Could have debris "temporarily" holding a valve open too.

There is Very low seat pressure on 4V heads due to low valve mass and lower total lift.

Also note that terminals are varnished and non conductive on many plugs - you should see scratches down to the bare metal on the used ones you pulled. Other use pogo springs on top of the terminals - I file the tops of the plug terminal on that application
 
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Originally Posted by Mad_Hatter
Did you double check the gap for s&g? What cylinder is it on?.. move the plug(s) to a different cylinder that's not experiencing a misfire and see if the misfire follows. If it does, it's the plug. If it doesn't and the misfire stays on the problem cylinder, well then it's likely the CoP. If this leads you to suspect the CoP, you could repeat the process with the CoP to see if the misfire moves to the new cylinder. (you could further repeat this with the injector on the problem cylinder also).

Now you said it was intermittent and at cold start up, so you may need to go through multiple start ups/cool downs to get some "data" in re to the misfire moving/staying.



The issue is that I don't know which cylinder it's on. My code reader won't show any data unless there's a CEL. Otherwise, i would have swapped an old plug in and ordered a replacement.

I pulled the coilpacks yesterday and lined the inside with some dielectric grease, making sure it didn't get on the contact point of the plug. As far as I could tell the rough idle was gone, BUT the engine was also still warm.

Let the engine cool down overnight and I'm currently pulling the plugs. So far so good, plugs look normal, some carbon build up near the threads but the electrodes are clean and like new
 
Originally Posted by avacado11
Originally Posted by Mad_Hatter
Did you double check the gap for s&g? What cylinder is it on?.. move the plug(s) to a different cylinder that's not experiencing a misfire and see if the misfire follows. If it does, it's the plug. If it doesn't and the misfire stays on the problem cylinder, well then it's likely the CoP. If this leads you to suspect the CoP, you could repeat the process with the CoP to see if the misfire moves to the new cylinder. (you could further repeat this with the injector on the problem cylinder also).

Now you said it was intermittent and at cold start up, so you may need to go through multiple start ups/cool downs to get some "data" in re to the misfire moving/staying.



The issue is that I don't know which cylinder it's on. My code reader won't show any data unless there's a CEL. Otherwise, i would have swapped an old plug in and ordered a replacement.

I pulled the coilpacks yesterday and lined the inside with some dielectric grease, making sure it didn't get on the contact point of the plug. As far as I could tell the rough idle was gone, BUT the engine was also still warm.

Let the engine cool down overnight and I'm currently pulling the plugs. So far so good, plugs look normal, some carbon build up near the threads but the electrodes are clean and like new

Are you using a OBD2 dongle w/app or handheld reader?

I use a dongle with the Torque App premium. When the engines running and completed all it's checks, I can go into the app and look at each cylinder misfire count. Does yours support this feature? I know not all ECU's will, so your ECU has to support this display to begin with...but if you are indeed having a bona fide misfire it (the misfire count and what cylinder) should be stored in the ECU.
 
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Pulled plugs and 2 of them were gapped too small(just below 0.5) so I corrected it and hopefully this fixes the issue.
 
Originally Posted by avacado11
Pulled plugs and 2 of them were gapped too small(just below 0.5) so I corrected it and hopefully this fixes the issue.

Could be something as simple as that, that's why I asked if you had checked them. Even on new plugs I check... here's hoping your misfire goes away....
 
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fixed the gap. Still a slight rough idle but for the most part it's good. Thinking maybe it's because I didn't gap them to be exact as the other ones. Just know they are between 0.52-0.54.

Also applied grease on the ceramic part of the plug.
 
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Originally Posted by avacado11
fixed the gap. Still a slight rough idle but for the most part it's good. Thinking maybe it's because I didn't gap them to be exact as the other ones. Just know they are between 0.52-0.54.

Also applied grease on the ceramic part of the plug.


But no more misfiring, right?...so we can say it wasn't the boots/CoP, yes? Wonder if the rough idle would smooth itself out with a road trip?

I thought maybe it was your gaps..I never trust the factory gap, I always check them.
 
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Originally Posted by Kawiguy454
On coil over plugs you need to coat them well with Dielectric grease and don't be stingy with it.. The high voltage coil overs will arc across the boots and cause the problem described. Especially if there is any kind of contamination in/on them.


A lot of people point to that as the reason that the early ford triton engines have constant issues with the coils failing. When I changed my coils I think I used a whole tube
 
Well Motorcraft ignitions have been sub par for decades.

On my 2001 bullitt they would arc to the intake. before it got to the plug

Lots of misfire counts.

Aluminum intake on the up spec Bullitt instead of composite resin
 
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