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 Post subject: 2012 kk cold start/rough idle, after a minute runs fine
PostPosted: Thu Oct 06, 2016 12:22 pm 
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Newb here. I usually just lurk in here trying to find the answers, but I haven't come up with anything definitive yet. I've googled my brains out trying to figure where to start here.

My KK (76k miles) starts up fine but has a really rough idle until warm then it runs perfect. My dash also dings like it's throwing a code but a light never comes on. It may ding 2 or 3 times before the car warms up (super irritating). I haven't seen anybody experiencing that particular event yet. This started about a week ago. It had happened intermittently for a while before that, but only lasted a few seconds. I've seen fixes for similar issues range from batteries to plugs to o2 sensors to AIC (I think this is actually inside the throttle body on my model). I'm leaning toward o2 sensor, but I'm a hobbyist at best.

To help narrow the chase, here are some things I'm not experiencing:
• jeep hasn't shut off due to rough idle (yet...)
• no ticking
• lights don't flicker with idle
• jeep runs fine when warm and warm starts

Trying to fix it myself, if possible. (sorry for the repost, just curious if any other 3.7s have experienced this)


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 Post subject: Re: 2012 kk cold start/rough idle, after a minute runs fine
PostPosted: Fri Oct 07, 2016 11:35 pm 
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Joined: Fri Nov 07, 2014 9:15 am
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Location: Pennsylvania
if you haven't already spark plugs should be changed. a fouled o2 sensor is unlikely, they either work, or they don't. also, just in case id check the battery and alternator output in volts.

to confirm my thought on the spark plugs though, try loading up the rig with maybe 300lbs of cargo and go up a hill. if she struggles (misfires) time for new plugs.

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Gen 5.5 A-Arms
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 Post subject: Re: 2012 kk cold start/rough idle, after a minute runs fine
PostPosted: Tue Oct 11, 2016 10:10 am 
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PALiftedKK wrote:
if you haven't already spark plugs should be changed. a fouled o2 sensor is unlikely, they either work, or they don't. also, just in case id check the battery and alternator output in volts.

to confirm my thought on the spark plugs though, try loading up the rig with maybe 300lbs of cargo and go up a hill. if she struggles (misfires) time for new plugs.


Thanks for the response. I took your advice and replaced the plugs yesterday. I also had the engine cleaned. Lots of carbon build up in there. And sadly, the problem persists. The plugs needed to be replaced anyway, so no harm no foul there. I just recently replaced the alternator (2 months ago) so I don't think that's it.

Since I'm getting misfires in cylinders 3 & 4, I'm wondering if it could be the coil pack. I know older models have coil packs on each cylinders, but as I learned yesterday, the KK only has coils packs on the driver side cylinders. I'm assuming they align with the passenger side cylinders. This would make sense since cylinders 3 & 4 share a coil pack, right? The OEM part is only 25 bucks. I may try replacing that and see if it makes a difference. Thoughts? If that's not the case, I'm not sure what to do.


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 Post subject: Re: 2012 kk cold start/rough idle, after a minute runs fine
PostPosted: Tue Oct 11, 2016 11:35 pm 
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Joined: Fri Nov 07, 2014 9:15 am
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Location: Pennsylvania
well as far as mis-fires after a spark plug change goes, id immediately look at the spark plug wires to see if the wire insulation was worn and the coil pack connections. to confirm if its a coil pack issue, swap the coil pack for cylinders 1&2 with cylinder 3&4.

the oem coil pack is $86. you'd better replace with oem since your most likely never to replace a coil pack there again. i would not trust an aftermarket coil pack. the price says it all.

make sure die electric grease are on the coil packs springs that touch the spark plugs as well as the spark plug leads.

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2012 Jeep Liberty KK 109k miles and stong
4" lift.
Gen 5.5 A-Arms
Maxxis 31x10.50x15

ATS42rle


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 Post subject: Re: 2012 kk cold start/rough idle, after a minute runs fine
PostPosted: Wed Oct 12, 2016 6:47 pm 
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^^^ x2 on what PA says. I was going to suggest swapping the coil pack to see if the problem follows it.

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