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  #1  
Old April 16th, 2018, 07:49
tchase tchase is offline
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Any spark plug gurus?

Ok... So it's time for a tune-up on the old XJ.

Wondering if anyone can offer any advice regarding what plugs to run and/or what the difference is between the 2 different plugs that are spec'd.

I have an '85 with a 2.5L long-block from an '02 Wrangler. Manifolds, fuel, and ignition systems are stock(ish) '85.

The OE plug for the '85 is Champion RFN14LY
The OE plug for the '02 is Champion RC12ECC

Do these 2 plugs physically interchange? My gut says go with the '02 plug as I'm sure it will physically fit but I really don't know much about plugs.
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Old April 16th, 2018, 08:19
RCP Phx RCP Phx is offline
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Re: Any spark plug gurus?

Here you go!
https://www.sparkplugs.com/Data/uplo...ing_System.jpg
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  #3  
Old April 16th, 2018, 09:22
tchase tchase is offline
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Re: Any spark plug gurus?

Quote:
Originally Posted by RCP Phx View Post
Thanks... But I can't get the link to work.
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  #4  
Old April 16th, 2018, 10:24
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Tim_MN Tim_MN is offline
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Re: Any spark plug gurus?

Since RFN14LY are available, that is what you should use.
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I'm starting to realize people on the Jeep forums are highly expert mechanics .....
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  #5  
Old April 16th, 2018, 11:11
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jeep ride jeep ride is offline
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Re: Any spark plug gurus?

Link not working
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  #6  
Old April 17th, 2018, 20:22
lawsoncl lawsoncl is offline
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Re: Any spark plug gurus?

Quote:
Originally Posted by jeep ride View Post
Link not working
Bascially identical except the RFN14LY is a hotter plug (14 versus 12). I suspect the 02 ECM runs things a touch leaner and hence needs a "colder" plug.? If in doubt, I would go with the colder RC12ECC plug as too hot can cause detonation and potential damage versus too cold just fouling the plug.

https://www.sparkplugs.com/product.aspx?zpid=8592 (RFN14LY)
https://www.sparkplugs.com/product.aspx?zpid=8519 (RC12ECC)
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  #7  
Old April 18th, 2018, 06:55
tchase tchase is offline
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Re: Any spark plug gurus?

Quote:
Originally Posted by lawsoncl View Post
Bascially identical except the RFN14LY is a hotter plug (14 versus 12). I suspect the 02 ECM runs things a touch leaner and hence needs a "colder" plug.? If in doubt, I would go with the colder RC12ECC plug as too hot can cause detonation and potential damage versus too cold just fouling the plug.

https://www.sparkplugs.com/product.aspx?zpid=8592 (RFN14LY)
https://www.sparkplugs.com/product.aspx?zpid=8519 (RC12ECC)
Perfect! Exactly the info I was hoping for. Thanks so much.
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