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Unread 11-18-2009, 02:51 AM   #1
madrabbitt
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what spark plugs on the 4.0?

I know the 4.7 has to have specific special copper core plugs, but does the 4.0 care?

I know the 4.0's in my cherokees ran like crap with expensive platinum and multi-point plugs, and prefered the cheap champion 1.99 truck plugs, but what about this newer 4.0?

I've had it for about 60 thousand miles, and the last thing the PO did was change the spark plugs to correct a cyl 5 misfire... dont know what plugs he used.

I've had 3 CEL's in the last few months. Cyl 5 misfire, Cyl 4 misfire, random/multiple cyl misfire.

All were on long trips, and all corrected themselves within a few days.

I figured spark plugs would be a good place to start.

The plugs that one of the fleet mechanics said to use are either champion plat power, PN#3034 , or autolite platinum AP985

both are stocked parts at my autozone, both are 2.99 each.

Anyone have any other suggestions?

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Unread 11-18-2009, 03:05 AM   #2
the88thpianoman
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Typically the cheap champion or autolite copper cores are the way to go, even on the new 4.0. You will not see any difference in performance or mileage with any type of fancy plug. However, a basic platinum plug should last quite a bit longer than the copper on our distributorless ignition system. On my last change I put in autolite platinum plugs because they were on sale for the same price as copper. It's been said on here that the single platinum plugs will last about 70k miles with our ignition.
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Unread 11-18-2009, 03:17 AM   #3
madrabbitt
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so knowing that the current plugs have around 65k miles on them, its probably time to change them then?
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Unread 11-18-2009, 07:50 AM   #4
Boodyrider
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The correct autolite plat is the APP985 for the newer 4.0, NOT the AP985. Lare amounts of real world experience say they DO make a difference, as did the Champion truck plugs for the older 4.0.
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Unread 11-18-2009, 12:02 PM   #5
96ZjBurner
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Well I have akways used bosch iridum fusion in my cars and currently that's what's in my 4.0 zj and I haven't had any problems since but I prolly will go with the coopper ones from champion due to the fact that's what 4.0s want and work best with
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Unread 11-18-2009, 01:58 PM   #6
madrabbitt
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ok, so not double tip plat, but plat tip and electrode.

i'll see what autozone has
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Installing HID's in stock housings is bad. Here is why.

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Unread 11-18-2009, 04:16 PM   #7
the88thpianoman
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Quote:
Originally Posted by Boodyrider View Post
The correct autolite plat is the APP985 for the newer 4.0, NOT the AP985. Lare amounts of real world experience say they DO make a difference, as did the Champion truck plugs for the older 4.0.
Care to elaborate on that? The plugs I have in right now are the single platinum AP985, not the double APP version. What differences have people experienced?
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Unread 11-18-2009, 04:45 PM   #8
madrabbitt
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yeah, i'd like to know more please.
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Installing HID's in stock housings is bad. Here is why.

"When you see someone who needs help, help them. When you see someone who needs a hug, hug them... Help those who can't help themselves." -Sgt Andrew Tingwall, NMSP. End of watch 6-10-2009
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