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Unread 01-27-2014, 11:22 PM   #1
Registered User
1998 ZJ 
Join Date: Jan 2014
Location: Severn, Md.
Posts: 1
Misfire 1998 ZJ

Hi everyone, My name is Josh, and I just bought a 98 ZJ from my uncle. I'm new to Zj's but not jeeps.This one has 183xxx miles on the original 4.0. When i first got it, it'd been sitting for roughly a year, following my uncle replacing the headgasket. One i started driving it i realized it had a slight misfire at idle but it smoothed out under load, and soon after,the check engine light came on. the code was for cylinder 1 misfire. i figured id replace plugs and wires, and the light went out and it ran fine. a few days later it returned to its previous state of running and the light came back on. my mechanic looked at it and ran tge code, and this time it was a misfire on cyl 1 and 3. He replaced the dist. cap and rotor and the light went off but the misfire continued. a compression test showed low compression on cyl 1 and average compression on cyl 3. Later that day the light came back on. he suspected a slightly bent valve. After driving it for a couple hundred miles and parking it overnight, i started it and to my surprise the light was off and the engine idled smooth. To me this meant it wasn't a bent valve, as this would cause a constant misfire vs the seemingly intermittent one that i was experiencing. later that day everything returned to the way it was...engine light in and rough idle.
thanks for bearing with me through the long description. Do any of you have an idea qhat this could be?

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Unread 01-28-2014, 02:09 PM   #2
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1997 ZJ 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 5,037
Welcome to JF.

Start with Zeejay's list:

On 7th PCM. Finally got a good one.
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