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Discussion Starter · #1 ·
Have a 97 wrangler with 4.0 in it. (before you jump and say the 97's and early 98's have a bad batch of valve springs... The motor is out of a 94)I have the code 43 misfire on cyl. 2,3,4,5 and 6. Somthing about primary Coil circut A and multipul missfires. Ive replaced cap, rotor, wires, plugs and ive tried 3 coils. The problem has gone away then comes back shortly after. Im leaning towards a pcm but wasen sure if anyones had this issue before
 

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Misfire

I had 2001 tj with 4.0 that would code misfire and after replacing everything except ECM still didn't fix it. After research it was the valve springs. I know how it sounds but that was it after replacement no codes after 10k miles. There was an article in J&P about it in the tech section. Hope it helps.
 

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Misfire

I want too make this as clear as I can so there is no misunderstanding, ok here we go. First off there is no bad batch of valve springs. I also had over 100k miles on the Jeep. I had a misfire code set at an idle as well as one being set at 75mph. Never once felt a miss? Replace plugs, coil pack, crank sensor, flush injectors and never could figure it out. In J&P magazine there was a Jeep Tech with the same problem on a 4.0 Cherokee. He replaced the spring on the cyl that coded and it fixed it. In turn I replaced all my valve springs and it fix mine. If it had not been for the Jeep Tech and a open mind I never would have fix it. As for your Jeep, I hope you fix it, I thought it I might be worth telling you if you get up against the wall and can't figure it out, think outside the box, it help me all though I couldn't wrap my head around it at first.
 

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Discussion Starter · #5 ·
Ok thank you, your right i should look outside the box on this one. However just as an fyi service bulletin number 18-22-98 is the bulliten for problem with the valve springs witch was released in december of 97. The bulletin involves installing revised valve springs and decarbonizing the cumbustion chamber.
 

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Service bulletin

Thanks for the info, I did not no that! I started with pulling the code, than I ran a compression test very first thing just to double ck. I was told that a weak valve spring could let the valve bounce just enough for the computer to detect a misfire. This went against my thinking but I guess it turned out to be the case for me.
 

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Ok thank you, your right i should look outside the box on this one. However just as an fyi service bulletin number 18-22-98 is the bulliten for problem with the valve springs witch was released in december of 97. The bulletin involves installing revised valve springs and decarbonizing the cumbustion chamber.
I wonder if it was the springs or the carboned up combustion chambers. I'd try decarbonizing it first, then do the springs.
 
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