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Unread 05-04-2014, 09:51 PM   #16
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2000 WJ 
Join Date: Apr 2014
Location: St. Petersburg, Florida
Posts: 2
I agree with ChrisHagar. The 4.0 recommends Champion RC12ECC coppers plugs gapped at .035. My 2000 WJ 4.0 came with Autolite platinums. I switched them out with the Champions and my engine runs fantastic. Go copper!

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Unread 05-05-2014, 07:53 AM   #17
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1999 WJ 
Join Date: Aug 2011
Location: Bethlehem, Pa
Posts: 308
+1 on that. champion copper.
1999 Jeep WJ, 78,072 miles new adco sway bar in rear. new rotors hubs and caliphers, new cv axles up front, Repainted-all black. steering system better stabilizer new tie rods and tubes. New shocks.
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Unread 05-08-2014, 11:21 AM   #18
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2004 WJ 
Join Date: Sep 2013
Location: Los Angeles, California
Posts: 56
The decal in my '04 4.0 specs NGK ZFR5N; they work great!
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Unread 05-08-2014, 11:35 AM   #19
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2004 WJ 
Join Date: Dec 2009
Location: Kansas
Posts: 14
Originally Posted by 86cj74.2L View Post
The coil on plug found in the 4.0 is more sensitive to plug type since the spark travels out one plug and in the other.
Don't know who told you that, but they lied to you.
All spark plugs, in all gas engines, fire to ground....not to another spark plug.

Last edited by mudpack; 05-08-2014 at 01:38 PM..
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