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Random Misfire Issue

718 Views 6 Replies 4 Participants Last post by  Mark_
Hi all!
I’m new to this forum but have an issue with my 2019 Jeep Cherokee Trailhawk that NO ONE can figure out. It has been to 3 different Jeep dealerships and multiple “ma and pa” mechanic shops and no one has been able to solve this.
So what I’ve noticed is ONLY in the winter my car has random misfires while idling only. Once I start driving it stops and will come back when I’m either parked or at a stoplight. The check engine light will either pop up with a message to “service stop start system” accompanied by the A with and arrow and exclamation point or just the check engine light will start flashing. The codes that are populating are P0300, or P1129. First time I had this issue was a little over a year ago (2021) around December and it only happened once last year and now this year it’s happened more times that I can count. The dealerships say bring it in but then they turn the car off and everything stops and when they turn it on they can’t make the misfire happen again so they say to come pick it up. From all the times it has been happening they have recommended I get an oil change, switch gas, get a new battery, flash my O2 sensors, reset the PCM, flash the system for any updates, and change my spark plugs and coil packs or have just said they have no clue and sent me on my way. I have done all of the maintenance listed above but my car still continues to misfire and none of my mechanic friends, or the shops can figure this out.
I was just curious if anyone on here has any more ideas on what it could be.
I have attached photos of what happens during the misfire and what pops up on my screen. I don’t know why but it’s not allowing me to upload the videos of it. Thank you for any responses and ideas!
Motor vehicle Automotive tire Automotive design Plant Gauge

Motor vehicle Automotive design Steering part Gauge Automotive tire

Blue Automotive tire Fluid Gadget Finger

Speedometer Car Vehicle Tachometer Motor vehicle
Speedometer Car Trip computer Tachometer Sky
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1st. Check your battery. Has it been replaced since 2019? Surprising what a weak battery issue can affect.
2nd Maybe an O2 cell gone bad?
3rd The misfire code is a common CEL code. Search for misfire and you'll find a bunch listed.
My 2014 had the P0301 code, cyl 1 misfire. Engine ran rough until warm up and smoothed out after. This condition has come and gone for awhile. Especially during cold weather although I havent seen for awhile, considering it was -10° last week.
The P1129 I'm not sure about. P1129 Jeep Code - Closed Loop Fueling Not Achieved Bank 2.

Read more: https://www.autocodes.com/p1129_jeep.html

Maybe try a few rounds of fuel injector/engine cleaner. I've used.....
Liqui Moly 2037 Pro-Line Engine Flush

Please let us know any follow-up/issue resolve.

Good Luck
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