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98 4.0 with misfire 3&4

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Old 04-04-2015, 01:57 PM
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Default 98 4.0 with misfire 3&4

Hey guys. brand new to the jeep nation and this site!

Anyways I've had my xj for about 6 months and I've come across a check engine light for a misfire on 3 & 4. I have new plugs, wires, cap/rotor. it has a pretty good loss of power but it's driveable. it misses at idle an smells really rich but once I drive it smooths out after 1500rpm.

it has 182,000 miles on it and I wanna try and get a general idea of what I should attack before I buy unnecessary parts. I'm hoping it's the fuel injectors. I haven't done a compression test yet.

what do you guys think? What's common for symptoms like this?
Old 04-04-2015, 02:04 PM
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Do the compression test.
Old 04-04-2015, 03:10 PM
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Check out this link.

http://www.autotap.com/techlibrary/d...g_misfires.asp

Chasing a random misfire myself. So far I've eliminated plugs and wires. Will be checking injectors tomorrow.
Old 04-04-2015, 11:28 PM
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I get the #3 misfire, and the PO used to get it, too. Ran into some other guys that have the same problem. We've all pretty much eliminated the plugs and wires. Best theory, is that since it is the cylinder in the middle of the inline 6, it is a heat sink issue. Haven't heard of anyone who has been able to successfully fix it.
Old 04-04-2015, 11:45 PM
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I had this issue and it was heat soak for me. I got heat insulator tape and put it on the bodies of the injectors. Then put a heat wrap on the fuel rail. Next I'll be upgrading headers and wrapping those also
Old 04-05-2015, 12:12 AM
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I don't know much about "heat soaked" engines/injectors but it's been doing this for 2 weeks now, and I've been driving it around. It's a pretty heavy misfire at idle. Whether the engine is cold or hot, doesn't matter. And it never goes away. Clears up after 1500rpm that once it goes back to below 1500 it misses again. So Idk if my stuff sounds like a heat soak or not.

Based off of quick reading people put insulator sleeves on their injectors. Pretty much true?

Also once Monday rolls around I'll do a compression test at my job.
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