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Discussion Starter #1
Hey guys, Wondering if anyone else can think of possible reasons to why i'm getting a misfire when doing a WOT pull.

The misfire happens during a WOT pull from about 2500 - 3500 RPM, It seems to be intermittent as during some pulls I feel like i'm getting full power and during others I feel a hesitation and my power feels like half of what it should be.

I'm running factory plugs with about 43,000 KMs on them, Re-gapped to .028", Checked the ignition coils and the springs were in the correct position when I re-installed them.

Should I be running a smaller gap with the factory coils? I've received the first update from the base tune and the misfire seems to be more apparent in the updated tune rather than the base tune; Assuming the update is more aggressive.

Misfire.PNG
Here is the PIDs from my log file

I've sent the log to Jerry @ BNR, He usually gets back to me on Sundays, thought I'd post here in case I can resolve it before he gets back to me.
 

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I had the same issue at 0.028", on a brand new engine and car...Misfired on the dyno. I gapped some BKR7s down to 0.024" and that worked well with 20psi boost pressure. But I don't rev over 5500rpms if I got WOT. Since then Jerry has sent me a revision with more timing and a leaner command afr so I might have to go with BKR8s. Jerry has never recommended a specific gap or plug so I'm guessing he's leaving that up to the customer to play with the gap to achieve a desired result.

XTremeRevolution why are you suggesting 0.020"? Wouldn't that have a negative effect on low rpm drivability? I've never heard of anyone going that low on gap from other highly modded Cruze owners... just curious...
 

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Sounds like I might be giving that a shot before going to a colder plug.
 
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I tried copper plugs gapped at .028" and they widened to .045" in two weeks and the car would barely go LOL.....not very practical if you ask me haha
 

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Before I load that hotter tune up tomorrow I'll gap the plugs down to .020". Then post back on here. Thanks
 

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Discussion Starter #11
I'm going to try the 0.020" gap later today, Nothing to loose I suppose... keep me posted on your findings, I'd like to solve the misfires before jerry gets back to me and suggests a weaker tune ;)
 

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Discussion Starter #12
So, changed the gap to .020 and the ECU is still reporting a misfire. Mostly from cylinder #2. I've been putting the same plugs back into the same cylinders to possibly identify a weak/failing plug.
The car seems to be behaving better now with a closer gap, also making me think that the coils are just stupid weak in my car for some reason.

Does anyone know the resistance spec of the coils so I can check if they are in spec? Or can that not be done with this type of coil pack?

Here is a screen shot of the misfire PID'S, I hit a maximum boost of 18 PSI with the ambient temp being ~3-4C and IAT averaging at 7C
020 Spark plug gap.JPG
 

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Dang that sucks man! Especially, at only 18psi. I bet a new OEM coil pack wouldn't be too pricey. I'm wondering how the electrode tips look? Maybe they're are chipped up a little and you need a magnifying glass to see their condition?
 

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I had the same issue at 0.028", on a brand new engine and car...Misfired on the dyno. I gapped some BKR7s down to 0.024" and that worked well with 20psi boost pressure. But I don't rev over 5500rpms if I got WOT. Since then Jerry has sent me a revision with more timing and a leaner command afr so I might have to go with BKR8s. Jerry has never recommended a specific gap or plug so I'm guessing he's leaving that up to the customer to play with the gap to achieve a desired result.

XTremeRevolution why are you suggesting 0.020"? Wouldn't that have a negative effect on low rpm drivability? I've never heard of anyone going that low on gap from other highly modded Cruze owners... just curious...
The BNR turbo guys are running 0.018. There isn't much of an effect on low RPM drivability IMO, but I'm also using copper plugs. The result may be different with OEM plugs.

So, changed the gap to .020 and the ECU is still reporting a misfire. Mostly from cylinder #2. I've been putting the same plugs back into the same cylinders to possibly identify a weak/failing plug.
The car seems to be behaving better now with a closer gap, also making me think that the coils are just stupid weak in my car for some reason.

Does anyone know the resistance spec of the coils so I can check if they are in spec? Or can that not be done with this type of coil pack?

Here is a screen shot of the misfire PID'S, I hit a maximum boost of 18 PSI with the ambient temp being ~3-4C and IAT averaging at 7C
View attachment 227578
Before you go off inspecting the coils, throw in a new set of BKR7E plugs. They will be under $10. That's all I run anymore.

My tune gets up to 21.5psi and I'm not misfiring. There's something going on with your car.
 

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Discussion Starter #15
Picked up the BKR7E's and tried a gap of .028, still no luck. Should I try a gap of .020 with them as well or start looking for a new coil pack? Also, what are the chances of the ECU reporting a false misfire?
The car seems to run fine, still sometimes get a really good pull and sometimes it feels stock... but it doesn't feel like complete miss of the combustion stroke
 

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Discussion Starter #16
I should add that this is a 2012 cruze automatic with only 43,000KMs on it, It sat for about 3 years of its life in a heated garage. There is no corrosion on the car whatsoever but maybe it wouldn't hurt to pull the coil boot and have a look at the connection to each individual coil? I'm kinda at a loss here, A new coil pack is ~$200 (Canadian Peso's) so I might just be better off saving up for the BNR coils to eliminate blowout all together.
 

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Discussion Starter #17
Did a little more digging into my logs, It appears that the misfire is only showing up after I do a hard acceleration, In this picture I captured a gradual throttle increase to WOT.
Could explain why I don't feel the misfire when I'm accelerating or its just the ECU actually displaying that there was a misfire later than "realtime".
020 gap graph.JPG
Let me know what you guys think
 

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That amount of misfires is nothing to worry about. Start worrying when you see numbers in the hundreds. All 1.4s have a few misfires here and there over a log.
 
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Discussion Starter #19
That amount of misfires is nothing to worry about. Start worrying when you see numbers in the hundreds. All 1.4s have a few misfires here and there over a log.
Thanks jerry, I've submitted my logs to you from this updated tune, like I said I don't feel the misfires so I wasn't to worried about it, Mostly just concerned about it effecting the performance.
 

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The BNR turbo guys are running 0.018. There isn't much of an effect on low RPM drivability IMO, but I'm also using copper plugs. The result may be different with OEM plugs.
So I gapped the BKRs down to .020" and drivability seems to be the same. Idle seems a little bit heavier but not much. Jerry's hotter tune is loaded. I'll get a WOT log after I put a hundred miles or so on the tune and post up the results.
 
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