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Old 12-08-2013, 09:50 AM   #1
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Default Stumbling Under Boost

I have recently installed a Flyin' Miata Voodoo II kit on my 1994. It also has a MSD ignition box, new Magnecor wires, new factory O2 sensor, and relatively new NGK plugs.

I am in the process following the tuning instructions and I am fairly certain that I have the A/F mixture and the O2 sensor spoof operating within specs but it is stumbling under boost.

I would imagine that there are a myriad of reasons that this could be so, but if someone would not mind pointing me in a general direction it would most appreciated.
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Old 12-08-2013, 10:39 AM   #2
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Which NGK plugs did you get? I had (what sounds like) the same problem. I went 2 steps colder on my plugs, and it accelerated smooth as can be under boost. But before that, it would stumble and fall on its face under any kind of boost.
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Old 12-08-2013, 12:43 PM   #3
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Furthermore, what's the plug gap?
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Old 12-08-2013, 12:47 PM   #4
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Furthermore, what's the plug gap?
yes, this ^

probably just as important, if not MORE important
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Old 12-08-2013, 03:25 PM   #5
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Thanks for the great responses. I have NGK BKR5EGP plugs installed. I set the gap the 0.034" per the instructions in the Flyin' Miata instructions. But now that I am re-reading them, it does say, "If the car still misfires, decrease the gap (to a minimum of .025")...".
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Old 12-08-2013, 04:21 PM   #6
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you can go lower than .025, and .034 is way too much gap
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Old 12-09-2013, 09:38 AM   #7
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you can go lower than .025, and .034 is way too much gap
Meh, I was running 12psi through EFR goodness on whatever random used VVT coils came on the engine from the junk yard with 0.045 gap.

What AFR are you running in boost?
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Old 12-09-2013, 09:49 AM   #8
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Meh, I was running 12psi through EFR goodness on whatever random used VVT coils came on the engine from the junk yard with 0.045 gap.

What AFR are you running in boost?
I got it to where the instructions tell me to -- around 13 or so at tip in then it gets down to around 11-10.5 at redline. Still toying with it though, and that is hard to do with the stumbling problem.
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Old 12-09-2013, 09:56 AM   #9
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If its missing the wideband is going to be reporting leaner than real life.
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Old 12-09-2013, 10:10 AM   #10
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Quote:
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If its missing the wideband is going to be reporting leaner than real life.
Ah, good point. Well, 'tis a process. Once I get it the miss fixed, I suppose I will be out tuning again.
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Old 12-09-2013, 10:14 AM   #11
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Quote:
Originally Posted by Leafy View Post
Meh, I was running 12psi through EFR goodness on whatever random used VVT coils came on the engine from the junk yard with 0.045 gap.

What AFR are you running in boost?
01+ cops are better than 94 coil packs.
I'd still bring it down lower than .034 is all I'm sayin.
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Old 12-09-2013, 11:29 AM   #12
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With my plug accidently gapped at .040 i wasn't blowing them out until around 16psi. Stock coils.
I was running out of fuel just before that point too.
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Old 12-09-2013, 11:37 AM   #13
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Would the fact that I have factory heat range (5) plugs installed make that much of a difference?
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Old 12-09-2013, 12:04 PM   #14
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it shoulnd't be a deal breaker at low boost. I've ran 5e's before with no issues.
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