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Unread 07-12-2002, 09:59 PM   #1
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spark plug gap

I did a search to try to find what the gap of a spark plug in a 99 4.0 litre, had no luck maybe one of you could help.

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Unread 07-13-2002, 12:06 AM   #2
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sorry to intrude but i have a question about spark plug gaps too.. Is it true that you can gain some power by widening the gap on the plugs? I heard it somewhere on some post but i wanna know if its true.
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Unread 07-13-2002, 12:51 AM   #3
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Did you try looking under the hood for the factory sticker? If it's still there and still readable it'll give ya the gap...
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Unread 07-13-2002, 06:59 AM   #4
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I know when I got my plugs from Napa, it actually had the gap printed on the recipt. I'm sure it is the same for most years, but my '97 FSM says a gap of 0.035" (0.89mm) for both the 4.0 and the 2.5l.
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Unread 07-18-2002, 08:11 AM   #5
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If you get the new BOSCH plugs you won't have to worry about the gap. Just get the double or the 4 prong ones and slap them baby's in. I got the doubles right now, feels no real noticeable difference. BUt you can't feel much of any performance gain with 33s and 3.07 gears!!
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Unread 07-20-2002, 07:59 AM   #6
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the gap is probably .035 for stock
you can open the gap up some, but may foul up and miss fire more often.
I put in a jacbs omni box, and that opens the gap up to .050, but put it a little closer to .045. and I have to change the plugs more often.
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