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Unread 03-13-2014, 04:56 PM   #1
drod77
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Spark plug Recommendations

I'm going to be replacing my spark plugs soon and was wondering what would be a good replacement. Do I go with oe or are there upgrades that I should go with. I have the inline 4.0.

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Unread 03-13-2014, 05:52 PM   #2
heitzman
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Champion Platinum.
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Unread 03-13-2014, 05:59 PM   #3
ezflip
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Not the platinums. Stick with champion coppers for the 4.0

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Unread 03-13-2014, 06:19 PM   #4
heitzman
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Correct. My mistake. Copper is recommended by Chrysler.
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Unread 03-13-2014, 06:41 PM   #5
fiveseven15
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same for the 4.7 non-HO? coppers?
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Unread 03-13-2014, 06:54 PM   #6
ezflip
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Originally Posted by fiveseven15 View Post
same for the 4.7 non-HO? coppers?
Correct. And the HO takes the platinums.

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Unread 03-14-2014, 12:26 AM   #7
Johnyre
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This should help you
http://www.wjjeeps.com/service/sparkplugs.htm
This place should be your first go to
http://www.wjjeeps.com/jmenu.htm
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Unread 03-14-2014, 04:12 AM   #8
gatorchin
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Two years ago when I got my 00 4.7, I had just joined the forum and of course read wjjeeps...they all screamed champion copper..well I was ordered a truck load of parts, couldn't get champions on rock auto at the time, so I got auto lite coppers..two years later after a small lift and bigger tires (put on last year) I saw my mpg drop to 11.3-11.7 on the evic...I finally put champion coppers in a few days ago, (and gapped them properly) and right now my evic is reading 15+ driving in this area ( mountains , lots of curves )..I hit the 4 lane and saw 18 mpg...now I know the evic is off, but just using it as a baseline reading, one can see how important it is to use the correct plugs
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Unread 03-14-2014, 05:26 AM   #9
86cj74.2L
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You can't even use it for a baseline.

Mine will say 17and math out to 14.5 one tank and read 17 again and math out to 20.7

The coil on plug found on the 4.7 will fire a 3/16 air gap without a single misfire and give a smooth idle. Changing from a autolite to a champion plug will not give you 2 mpg increase. Fuel quality and driving habits will though.

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. Sometimes they don't like foreign from ground arm to the center electrode of the fine wire fancy spark plugs without a miss. Copper anything is best for the 4.0 and its wasted spark setup.
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Unread 03-14-2014, 10:01 AM   #10
ChrisHager
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4.0
Champion RC12ECC (P/N 438). Also rumored from the TJ guys, Champion RC12PEPB5 (P/N 7034).
Gap: 0.035


4.7
Champion RC12MCC4 (P/N 439)
Gap: 0.040


4.7 H.O.
Champion RC7PYCB4 (P/N 3340)
Gap: 0.040
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Unread 03-14-2014, 02:37 PM   #11
corpulent
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For the '04 4.0
NGK
4.0L Plug: MoparŪ P/N SP000ZFR5N Gap: 0.035 Torque: 26-30 ft. l
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Unread 03-14-2014, 02:55 PM   #12
corpulent
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Duplicate post
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Unread 03-14-2014, 02:59 PM   #13
cjcyr8
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I used OEM NGK coppers on my 04 WJ 4.0.....AWESOME
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Unread 03-14-2014, 08:25 PM   #14
2ndhandWJman
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It's very simple. Open your hood and look at the emissions decal, it will tell you what plugs the Jerp left the factory with. Go to a Jerp dealership and buy those exact plugs. It really is THAT simple.
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Unread 03-29-2014, 07:15 PM   #15
kdsimmons19
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Quote:
Originally Posted by 2ndhandWJman View Post
It's very simple. Open your hood and look at the emissions decal, it will tell you what plugs the Jerp left the factory with. Go to a Jerp dealership and buy those exact plugs. It really is THAT simple.
this guy is onto something. i recently had a guy tell me that since the sparkplugs i bought were so cheap (about $3 a piece on rock), i likely bought the wrong thing. look at the emission decal and the box of new plugs, same damn number.
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