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Old 05-09-2010, 01:00 PM   #1
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Default Backfiring/popping while under load

Hey guys,

I've got my car running pretty well most of the time. I do occasionally get backfiring and popping while under load in boost. I've already gaped my stock plugs down to 0.030". It seems to happen only when the engine is just warmed up but not driven hard. After a few hard pulls and more aggressive driving it seems to go away. My reading and searching leads me to believe that it sounds like it would be spark blowout. Is my spark too small at this gap? If this is the case, what plug should I be using? A step colder or a step hotter? I'm on the stock spec right now.
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Old 05-10-2010, 09:29 AM   #2
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if you had spark blowout, your car would pull like ****, and you'd be able to feel the misfires.

What does your AFR gauge say when this is happening?
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Old 05-10-2010, 09:38 AM   #3
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You should be using BKR7E's.
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Old 05-10-2010, 09:58 AM   #4
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I just checked and I am using BKR5E.
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Old 05-10-2010, 10:22 AM   #5
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5's are too hot. What is your plug gap?
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Old 05-10-2010, 10:32 AM   #6
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Plug gap is 0.030". I haven't really been driving the car much because I've gotten a bit lazy with fixing the exhaust to frame rattle. I'm gonna get some 7's in the mean time. Does anyone know the new BKR7E part number off hand? I'm searching for it at the moment.

EDIT: Got it here for future reference NGK 4644

Is there any relationship between plug gap and colder plugs? Does a colder plug generally require a smaller gap? Or do these not affect one another?
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Old 05-10-2010, 11:02 AM   #7
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That's too much plug gap if you're on the stock coil.
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Old 05-10-2010, 12:07 PM   #8
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I am on stock coils. What should I be reducing the gap to, 0.025" or even less? I thought 0.030 was what I've seen people recommending. Stock gap is 0.043" isn't it - 1.1mm?
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Old 05-10-2010, 12:32 PM   #9
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I had to run .020" when I had the stock 1.6 coils at 16psi or it would blow out.
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Old 05-10-2010, 01:11 PM   #10
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Thanks, I'll give 0.020" a go on the new plugs. Is backfiring/popping and slight tugging while giving throttle a typical trait of spark blowout? I know there could be a lot of other answers, but everything 'appears' to be ok, so I'm looking for the most obvious answers.
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Old 05-10-2010, 01:30 PM   #11
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Quote:
Originally Posted by dgmorr View Post
Is there any relationship between plug gap and colder plugs? Does a colder plug generally require a smaller gap? Or do these not affect one another?
There is no significant relationship between the two. I had a bunch of other **** typed out that I deleted, but that's the short answer.
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