Misfire issues (with precision coils)

Ztuck45

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May 16, 2017
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2010 335i
So I need some help. I've been having random misfires that I believe is originating from my spark plugs.

I'm running the precision ignition system on e50 and usually 17-20psi. I had been using NGK 95770 gapped to .022 which worked fine for a while but I started getting random misfires under load on one cylinder at a time. When I pull the plugs this is what it looks like. (Picture)

I recently switched to Autolite XP 5682 gapped to .022 as well. These actually felt better than the NGK's power-wise but literally the same day I got a cylinder 6 misfire. I havnt pulled this plug to inspect it yet.

At this point I'm not sure what the problem is.

IMG_2863.JPG
 

JAperformance

Specialist
Feb 13, 2017
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09 335i
I'm using 95770 at .025 gap 30psi no issues so far. Check and see if it's not tune related. As I stated in the other post, I did have misfire problem with JB4 but it was fuel related on bef settings.
 

Ztuck45

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May 16, 2017
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I'm using 95770 at .025 gap 30psi no issues so far. Check and see if it's not tune related. As I stated in the other post, I did have misfire problem with JB4 but it was fuel related on bef settings.

That's a possiblilty, I switched to an emp tuning remote tune the same time I did these coils
 
Jun 8, 2017
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Magnolia Texas
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The plug in your picture has a cracked Porcelain insulator. Those black lines are carbon build up where voltage leaked through. I don't know about the other plugs but any plug that came out looking like that was a sure misfire for this reason. The voltage will jump out of the defective insulator to ground if that's the least restrictive path, i.e. under boost. Be extremely careful with plugs. Treat them like glass. If the boxes have any evidence of dropping or rough handling leave those at the store. They always need to be inspected with magnification before installation, especially if mail ordered. Always order or buy an extra and if any one suffers a drop that makes a loud noise put it aside and use the spare. When installing them be sure your socked and extension is as strait as possible and don't over tighten them. If you hear a pop or snap when torquing them down most times it just cracked like yours and needs to be scrapped. On the N54 the plugs are very easy to access but if you've ever owned or maintained a high performance engine where plugs take hours to replace you don't take chances and you rarely suffer misfires from broken insulators. Just experience talking.

Vernon
 

Ztuck45

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May 16, 2017
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Thank you for the input. I'm going to replace my cylinder 6 plug and use dielectric grease on all of my spark plug boots and report back with the results.
 
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V8bait

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Nov 2, 2016
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Thank you for the input. I'm going to replace my cylinder 6 plug and use dielectric grease on all of my spark plug boots and report back with the results.

Yeah, welcome to high voltage coils, they will find a path to ground lol. You should combine with the other thread it's the same thing. Fwiw I'm using .031" on one step cooler plugs at 20-21psi no issues for 7 or 8k miles but as power goes up it's more important to have your bases covered. This is a pretty good video segment, q-tip to apply grease around boot without touching the terminals https://youtu.be/-542IYGBbpg

BL coil users should take note as well since the Audi coil is also much higher voltage than factory.
 
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Jeffman

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Jan 7, 2017
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Thanks Justin. Just a reminder for those, like me, who never used dielectric grease before on an ignition system... Dielectric grease is an INSULATOR. It only touches the spark plug boot and the porcelain insulator, NOT THE WIRE TERMINALS.
 
Feb 1, 2017
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Yeah, welcome to high voltage coils, they will find a path to ground lol. You should combine with the other thread it's the same thing. Fwiw I'm using .031" on one step cooler plugs at 20-21psi no issues for 7 or 8k miles but as power goes up it's more important to have your bases covered. This is a pretty good video segment, q-tip to apply grease around boot without touching the terminals https://youtu.be/-542IYGBbpg

BL coil users should take note as well since the Audi coil is also much higher voltage than factory.

We haven't had any issues yet, even at .035"

The R8 coils do put out some crazy voltage tho, I tried using a spark plug voltage simulator before and instead of jumping the 60kv gap it would go through the clear plastic housing and about an inch away to the metal sleeve. Tried covering the metal sleeve with electrical tape too and it went through that. I think I have a video of it somewhere, pretty impressive.
 
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V8bait

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We haven't had any issues yet, even at .035"

The R8 coils do put out some crazy voltage tho, I tried using a spark plug voltage simulator before and instead of jumping the 60kv gap it would go through the clear plastic housing and about an inch away to the metal sleeve. Tried covering the metal sleeve with electrical tape too and it went through that. I think I have a video of it somewhere, pretty impressive.

Yeah the R8 have lots of voltage and the similar snap terminals to the wires PR use. I'd use silicon grease on them too for high power builds. My car is at .031 (factory plug gap) just fine but depending on the plug, boost, etc sometimes the gap is harder than through the shielding, thus this happens. COP is generally weaker so doesn't have the issue as much. High power coils and power dense motors take a little more work.
 

Cheezy

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Nov 7, 2016
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I'm having a similar misfire issue in cyl6 but I'm still on OEM coils. I wonder if my issue could be a damaged insulator (plugs have 100miles on them, mail order from bms). I changed a coil pack to rule it out and nothing changed, misfires under load at 6000+ rpm
 
Jun 8, 2017
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Magnolia Texas
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It could very well be. A damaged insulator will cause a mis-fire on the weakest ignition system you'll find and no amount of dielectric grease will prevent or eliminate a misfire once an insulator has broken. It just physically becomes the easiest path to ground since the base of the plug is the closest ground and you can't fill the crack with dielectic.

Vernon
 
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Cheezy

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Nov 7, 2016
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It could very well be. A damaged insulator will cause a mis-fire on the weakest ignition system you'll find and no amount of dielectric grease will prevent or eliminate a misfire once an insulator has broken. It just physically becomes the easiest path to ground since the base of the plug is the closest ground and you can't fill the crack with dielectic.

Vernon
Thanks Vernon! This really didn't even cross my mind, I was just going to blindly change the plug and then call for injectors next! I'll be sure to keep my eye out for cracks when I pull the plug and in the future when I swap them again!
 

AndersS

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Dec 10, 2016
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For us who didn't even knew that there is a product named Dielectric grease, could someone perhaps make a little DYI about it or just a MS paint-drawing.;)
How much grease is needed.? How to place it? On the porcelain insulator and also inside the coil? Or both.?
 

Kommodore

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Nov 5, 2016
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Cactus Farm
R8 coils come with grease in them out of the box.

Yeah the R8 have lots of voltage and the similar snap terminals to the wires PR use. I'd use silicon grease on them too for high power builds. My car is at .031 (factory plug gap) just fine but depending on the plug, boost, etc sometimes the gap is harder than through the shielding, thus this happens. COP is generally weaker so doesn't have the issue as much. High power coils and power dense motors take a little more work.
 

[email protected]

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Nov 5, 2016
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Thanks Justin. Just a reminder for those, like me, who never used dielectric grease before on an ignition system... Dielectric grease is an INSULATOR. It only touches the spark plug boot and the porcelain insulator, NOT THE WIRE TERMINALS.
This stuff is slathered all over electical connections on boats, outdoor installations etc to water proof the connections. It will not have any negative effects if its on the connections in MY experience, and I have used it for years. I just watched that video. I never stuff it inside connectors like that. But I am not super careful either. I just put some on the tip of the coil, and install it.
 
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V8bait

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Nov 2, 2016
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For me it serves two purposes, it seals the connection and allows the silicone boot to be easily removed. I am in exact agreement with Tony. I have never been careful with it and have never had it cause a diminished spark.

No matter how you use it it's better than not using it. If the plug is fully engaged it shouldn't matter as the grease will be pushed out of the way. It is important to get the wire fully engaged though, a blunt object like pliers helps to push them on.

In all of this fun I found something interesting. There have been three people who have had issues with the flash time option (disabling multispark) leading to misfires. One or 2 are likely DME related, and one is likely a big boost leak at the PI-head interface (he also runs rough at start and has been dropping ALL of its timing, since before these new coils). All 3 do better with multispark on. I find it interesting as you shouldn't *need* multispark unless there's an issue to begin with, so I've been trying to brainstorm situations where multispark would mask issues single spark doesn't. Any of the others here want to throw some ideas?

I think a big vacuum leak near the head is one. Multispark would fire a super lean mix in one cylinder after tdc I venture to guess (after a lean miss technically occurs on the first spark), since pressure would be dropping with a hotter/more combustible mix of e85. Might not even see the lean bank in logs if you're on jb4. Maybe this carbon tracking too, second spark when the plug gap is less voltage than the track? What other problems can be hidden by multispark?