New plugs in 2012 Frontier

MolaKule

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I had the Spark plugs changed at 78,000 miles since the idle was getting a bit rough and fuel economy was dropping somewhat. The plugs that were pulled looked good but two had slightly higher resistances than average. None of them appeared overheated or had any deposits whatsoever. New NGK Iridium's (LFR5AIX ) went in and now idle is very smooth.
 

MolaKule

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Originally Posted by Dave_Mark
Were there NGK Rutheniums available for your application?
I checked all four local parts stores and they could order them but it would be about a 3-5 day delivery. However, I needed the plugs changed before I go a short trip this weekend (weather permitting frown )
 
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Sounds like the time for plug service. The Impedance in the RF resistor doesn't matter much since its very high voltage and you are jumping a spark gap. You do want read continuity there though as evidence the resistor didn't burn out. Typically over time contaminants build up around the external insulators and they break down during high humidity and certain engine loads. The spark doesn't really want to jump the gap if its easier to bridge across under the plug boot and crawl along the alumina insulator. Glad to hear it ran better after the tune smile .
 
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Originally Posted by Marco620
Im installing NGK Ruthenium plugs this next oci. Im sure they are good for at least 50HP!
From what I've seen on plug changeout video on YouToob for the latest subaru FB20, they employ these plugs and I feel I'd be a dope if I change them out at 60K as Subaru advises. That's a junky old school Pt plug service interval. So what do I do? I have one of those (joke?) lifetime engine warranties from the dealer, that requires all service in the manual to be performed. I guessing the ruthenium is alloyed with Pt to increase hardness and toughness of the Pt thumbnail on the GND electrode on these plugs. This is likely where the increase ignitability comes from. With more prevalent wideband Lambda control we may see leaner part-load mixtures than in recent past with simple feedback and mapping.
 
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Originally Posted by MolaKule
The plugs that were pulled looked good but two had slightly higher resistances than average.
What is the usual degradation mechanism? Is it center electrode micro-cracking due to vibration over time? What resistance do they have new, versus the highest allowed used?
 
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my 11 fronty 4.0 only has 36 thou on it but prolly change at 50 thou. girlfriends 08 1.8t passat got plugs at 50 thou and several more mpgs!
 

MolaKule

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Originally Posted by Sierra048
Is that the 4.0 V6. If so, how did you handle the passenger side plugs? Did you remove the air plenum to get to them?
Yes, the Plenum had to be removed. A 3.5 hour job in total. Driver side plugs are a no brainer as the coil-overs are staring you right in the face/
 
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MolaKule

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Originally Posted by paoester
Originally Posted by MolaKule
The plugs that were pulled looked good but two had slightly higher resistances than average.
What is the usual degradation mechanism? Is it center electrode micro-cracking due to vibration over time? What resistance do they have new, versus the highest allowed used?
New plug cold resistance averaged 3.5k. Used plug resistance averaged 4.1k. The highest used plug resistance was around 6.7k cold, but was likely much higher when hot. Plug resistance really shouldn't matter as the spark voltage is very high, but if the ceramic resistor cracks internally a slightly higher voltage is needed at the tip for firing. The resistor's main function is to dampen any RF emissions to the electronics. Only one plug had a large gap as the center electrode had worn down which was interesting and unexpected. This was probably the one causing the rough idle at high-idle compression..
 
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Originally Posted by MolaKule
Originally Posted by Sierra048
Is that the 4.0 V6. If so, how did you handle the passenger side plugs? Did you remove the air plenum to get to them?
Yes, the Plenum had to be removed. A 3.5 hour job in total. Driver side plugs are a no brainer as the coil-overs are staring you right in the face/
Thanks. Yes, that's what I had to do as well.
 
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My NGK were factory just the new Rutheniums. Looked the same. I didn't have to take anything off. Just the passenger intake brace. NOT the entire intake.
 
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