91 yj 4.0 H.O. - Jeep Wrangler Forum

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Old 02-16-2013, 10:45 PM   #1
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91 yj 4.0 H.O.

My wrangler started lopeing at low speed but idles smooth and runs like a scalded Dog at highway speed anyone have any ideas.
It has the 4.0 H .O. and 5 speed manual trans.

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Old 02-16-2013, 11:01 PM   #2
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Sounds like its running lean. Pull the plugs and number them. Look at each plug and check the color of the core carefully.

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Old 02-17-2013, 09:24 PM   #3
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Here is a plug chart to help out.
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