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#4552049 - 10/23/17 02:34 PM spark plug gap question
NissanMaxima Offline


Registered: 10/21/15
Posts: 187
Loc: co
Hello all:

I need to change out the spark plugs on my Maxima with OEM recommended NGK platinum plugs and had two questions:

1. gap: my spec is 0.039" to 0.043". The NGK plus come pregapped at 0.044" and they tell me there will be no performance difference regapping to 0.040 (not sure why they chose this value). Honestly I would rather not mess with the NGK gap if this is true because I have regapped plugs in the past and it can be challenging. However, if I take the midpoint of 0.041", isn't 0.044, or 0.003" difference, a bit excessive? I have read that spark plug gap increases with use so why start out with a higher gap in the first place. To further try and educate myself, I then conducted a Google search looking for data on engine performance/efficiency as a function of spark plug gap and turned up nothing. It will be interesting to measure the gap of the plugs I remove however I don't know of course the exact value they were set to at the Nissan factory and maybe they didn't regap the OEM NGK plugs! In other words, I don't know the original gap value.
2. torque: my spec is 14-22 ft lbs. Why is there such a large range? I'm going to buy a good torque wrench. Should I just go for the midpoint value of 18 ft lbs?

Thanks

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#4552057 - 10/23/17 02:41 PM Re: spark plug gap question [Re: NissanMaxima]
THafeez Offline


Registered: 08/15/16
Posts: 651
Loc: New Jersey
For the torques specs, I would say snug it up. Last time I used a torque wrench and went by oem standards, the plug was a bit loose and I was having rough starts. Tightened with 2 fingers after and all was good..

They give a range because a "snug fit" may vary from engine to engine. I realize that now because Toyota only gives one value for my car. Nissan probably gave a range because they knew some would need 19 while others would need 14. Snug it up and then use the torque wrench at 14, 15,16 and so on increments to see what your engine has if you so choose. Personally I wouldn't bother.

As for the gap, I would NOT try to regap it because you risk breaking the tip and the precious metals come off from the gapping tool as well. If you're really worried (I wouldn't be) only use feeler gauges. Don't use the cheap circle gap adjusters at autozone. I'd trust the NGK gap and leave it alone.

I remember the first time I did spark plugs I was worried about gaps and threading it wrong etc, it gets easier after that. It helps to put the plug on a small piece of hose and thread it backwards to seat it, then spin forward slowly. Good luck.
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#4552060 - 10/23/17 02:44 PM Re: spark plug gap question [Re: THafeez]
WobblyElvis Offline


Registered: 09/23/14
Posts: 1345
Loc: Toronto Canada
Originally Posted By: THafeez
For the torques specs, I would say snug it up. Last time I used a torque wrench and went by oem standards, the plug was a bit loose and I was having combustion problems. Tightened with 2 fingers after and all was good. As for the gap, I would NOT try to regap it because you risk breaking the tip and the precious metals come off from the gapping tool as well. If you're really worried (I wouldn't be) only use feeler gauges. Don't use the cheap circle gap adjusters at autozone. I'd trust the NGK gap and leave it alone.


+1

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#4552095 - 10/23/17 03:21 PM Re: spark plug gap question [Re: NissanMaxima]
PandaBear Online   content


Registered: 08/05/02
Posts: 14219
Loc: Silicon Valley
Plug gap has to consider electrode diameter as the overall calculation. If you are using fine wire plug you can go with a wider gap and still fire. Seriously, 0.004" is not going to make a difference.
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#4552103 - 10/23/17 03:28 PM Re: spark plug gap question [Re: NissanMaxima]
03cvpi Offline


Registered: 03/04/07
Posts: 198
Loc: Minneapolis
I would re-gap to 0.040. Always to the mid or smaller end of the factory range. The larger the gap, the harder the coil has to work to fire the plug. Have seen many COP units fail because the gap increased 0.005 beyond range.

Electrode diameter has very little to do with air gap. Air gap is the critical measurement.

Have also seen a number of problems with VVT, plug misfire and poisoned cats because the air gap was beyond spec, usually by 0.008 to 0.012


Edited by 03cvpi (10/23/17 03:36 PM)

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#4552122 - 10/23/17 03:51 PM Re: spark plug gap question [Re: NissanMaxima]
HoosierJeeper Offline


Registered: 11/23/16
Posts: 1276
Loc: WI
x2 on the above for gap and for those torque specs are for dry threads, I'd recommend using anti seize but that throws the torque specs off. I'd snug them by hand and then with the ratchet give 1/4 turn more.
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15 Jeep KL Limited V6: Formula Shell 5W20
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#4552159 - 10/23/17 04:35 PM Re: spark plug gap question [Re: NissanMaxima]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
I would gap to 0.040 so as the electrode wears the gap will widen to the end of the acceptable range. If it's at the end of the acceptable range
to start with and the electrode wears you could put more stress on the coil and/or set a code on some ECU's if the coil is a bit weak, or worse cause a slight misfire condition.

As for the snugging. I like to put them in with barely any pressure on the ratchet and when it stops under this light force, I snug them a 1/4 - 1/2 a turn. (Don't over-tighten, no more than one hand's force at the bottom of the ratchet while turning this last little bit, so you have an idea of the pressure.) Just enough to compress the sealing washer slightly for a good seal.



Edited by StevieC (10/23/17 04:36 PM)
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#4552216 - 10/23/17 05:29 PM Re: spark plug gap question [Re: NissanMaxima]
slacktide_bitog Offline


Registered: 03/20/08
Posts: 6162
Loc: USA
What year Maxima? Is this a 4th gen Maxima? 95-99? I have a 96 I30 smile

I used 18 lb-ft when I changed them in my car, but I used Denso iridium. But I believe the stock NGK part number is 2647 aka PFR5G-11, where the 11 indicates 1.1 mm or .0433 in.

Just use them as-is with the prset gap and don;t worry about it again for a long time smile

At least we have cutouts int he intake to access the back plugs! Otherwise, I'd recommend iridium!

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#4552225 - 10/23/17 05:33 PM Re: spark plug gap question [Re: NissanMaxima]
mk378 Offline


Registered: 09/27/15
Posts: 1420
Loc: USA
Modern cars don't care much about the gap. It's typical to change out long-overdue spark plugs that have worn to twice the original gap but the engine was still running fine.

Gasket seal plugs are usually tightened by angle not by torque. Instructions often on the box.

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#4552238 - 10/23/17 05:45 PM Re: spark plug gap question [Re: NissanMaxima]
Silk Offline


Registered: 07/26/03
Posts: 4560
Loc: New Zealand
The gap is 1.1mm, they just guess a number for imperial that is close enough. They are gapped correctly.
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#4552242 - 10/23/17 05:48 PM Re: spark plug gap question [Re: NissanMaxima]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1810
Loc: Saskatchewan, Canada
It's not recommended to re-gap platinum or iridium plugs. You risk cracking the electrode; both materials are very brittle as well as very hard.

0.44 is fine for any electronic ignition. Some are OK at 0.60" There is no real difference between 0.43 and 0.44", unless there is something seriously wrong with your ignition system and/or ECM. And I mean seriously wrong.

You should check the gap, though. Sometimes the wrong plug gap gets into the package. Return them for properly gapped units if that happens.
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'01 PT Cruiser [Mobil1 0W-40]

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#4552254 - 10/23/17 06:01 PM Re: spark plug gap question [Re: slacktide_bitog]
NissanMaxima Offline


Registered: 10/21/15
Posts: 187
Loc: co
Originally Posted By: slacktide_bitog
What year Maxima? Is this a 4th gen Maxima? 95-99? I have a 96 I30 smile


Yes! Fourth generation 95 in beautiful shape still - first time changing plugs in this car! You are also correct about the recommended plugs as the part number you gave is exactly the same as in my factory service manual. I did not realize the 11 in the part number indicated 1.1mm or 0.043".

-----
Seems the board is split between regapping and running as is. This is why I had hoped to see some articles or papers on true effect of increased gap on efficiency/performance. My sense was that if use increases gap and increased gap degrades efficiency/performance, why not start at the mid-range of the sped gap? But I've not heard or read anything to substantiate that. I'm hoping that the new plugs will restore some performance I used to have at lower elevations when the car was new but perhaps gap really doesn't matter (other than perhaps making the coils work harder as one member mentioned).

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#4552304 - 10/23/17 06:33 PM Re: spark plug gap question [Re: NissanMaxima]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
Go by what the manufacturer of the car recommends.

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#4552318 - 10/23/17 06:47 PM Re: spark plug gap question [Re: NissanMaxima]
spasm3 Offline


Registered: 05/30/10
Posts: 8652
Loc: North Carolina
My olds calls for .060.
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#4552402 - 10/23/17 08:19 PM Re: spark plug gap question [Re: NissanMaxima]
GMBoy Offline


Registered: 11/22/04
Posts: 7702
Loc: Texas
I agree with everyone mentioning regap to .40. You are only touching the ground strap, not the fine delicate electrode so those saying you cannot gap these are incorrect. You must be careful for sure!

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