Last week as I was driven to work my 2005 130000 miles started doing some weird things. The speedometer and the tach started fluttering and the gauge lights started dimming in tune with the fluttering. It stopped after a few minutes. Yesterday I wnet and started it and it started idling rough and when I went to drive it it started hesitating and sputtering then it cleared up and ran fine but, the check engine light came on. I took it to a local shop and they scanned it and we got a code P0300 multi-misfire. They suggested changing the plugs and running a fuel additive thru it and I did. It ran well for the rest of the day. Today I started it and it started running rough again. I took it to a different shop and they scanned it and they got the same code P0300 and a new one P0172 Bad Oxygen sensor. Could the cause the rough idle? Any other suggestions?
Misfire
- Thread starter pyrotaz
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CzarKJ
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What plugs did you use? Copper is what works best for liberties.
martin_metal_88
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The bad O2 sensor could be the problem. I would change them anyway since they go for like 40$ each. What kind of plug do you have? some fancy platinum that wont work well in a libby or copper plug ( actually the only one that work well in a liby, and the cheapest 
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)
Snail Farmer
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Yes the O2 sensors can definitely cause the misfires. Make sure to replace them with NTK only. Do not use Bosch or any other cheap knock off.
martin_metal_88
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For the price I would say all four.
Snail Farmer
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To fix the issue, only the front two (pre cat) need to be replaced. The computer adjusts based on the readings it gets from them. The back two (post cat) send readings only. The computer does not adjust anything based off those readings. When I had this problem, I replaced all four but it's not necessary unless you want to.
tjkj2002
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While true it is extremly rare and highly unlikely as even a totally dead O2 sensor(or removed O2) will just send the PCM back into open loop.In 15 years I've seen it happen once and was not the only issue causing the misfire also.I had a '07 KJ with a constant misfire on 3 cylinders(1,3,6) and nothing changed till the cats where replaced,that was about 4 months ago.
Snail Farmer
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It happened to my KJ and there were a couple of others on here that had the same problem shortly after me and that was the cause also. Seems to be one of the main causes of the P0300 code from what I've seen. I threw parts left and right at mine when it happened because I thought the same thing: no way it could just be an O2 sensor. But ever since I replaced them, my KJ has been smooth. It's been a year and a half since I replaced them, and still no misfires or codes. I'm not saying it's definitely the problem in the OP's case, but O2 sensors aren't expensive, and my general rule to a problem that has no definite answer is do the cheapest first.
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tjkj2002
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Sounds like you had slightly lazy O2's and new ones are still keeping it in that 1.5 ratio emission zone,I'd be expecting cat failure in the near future.
Searcher67
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Doesn't this misfire issue seem to be a habit with the Libertys? I mean, don't you think that if 90% of the Libertys are throwing misfires, Chrysler should be doing something about it?
dude1116
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I think most vehicles have issues like that, especially popular ones. I remember my buddy's 4.0 XJ misfired on 4 cylinders.
I'm knocking on wood while I say this...but I haven't gotten any misfires yet and I'm at 105k... :hidesbehindsofa:
Searcher67
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I have always had misfires, usually only when first starting the Libby. My head gasket went at 120XXX, then again at 135XXX (poor workmanship) (NOT ME, NOT ME). Now, it seems that I am getting the misfires at start up and while idling in traffic.. Although, mine is not throwing codes, it still bothers me. My Liberty is 12 and not one person believes she's that old. Some don't even realize its a Jeep, which is heartbreaking!
The body is perfect and the paint shines like its sitting in the showroom. The interior is great.. I cannot believe that with the minimal upkeep I have provided over the years she still looks and acts this good. She's been through hell n back, up and down many a trail and never gave a lick of trouble, UNTIL that first head gasket went. Then it seems I am getting paid back for all those years of no fixes..
I understand the front end parts going bad (finally). But those damn misfires really got me down.. I am seeing a new Unlimited Sport in my near future..
The body is perfect and the paint shines like its sitting in the showroom. The interior is great.. I cannot believe that with the minimal upkeep I have provided over the years she still looks and acts this good. She's been through hell n back, up and down many a trail and never gave a lick of trouble, UNTIL that first head gasket went. Then it seems I am getting paid back for all those years of no fixes..
I understand the front end parts going bad (finally). But those damn misfires really got me down.. I am seeing a new Unlimited Sport in my near future..
tjkj2002
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In bold is the key words......................
You want engine issues buying a JK with the 3.6 is a sure way of getting engine issues caused by multiple engine misfires which require new heads to fix.
My KJ is also almost 12 years old,beatin to death and never had one misfire ever.
Searcher67
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By "minimal upkeep" I didn't mean I didn't more than properly maintain my Jeep..
It got the best care money could buy...I only meant that I never had any part failures, such as water pumps, front end parts, drive train parts ETC..
Tires, brake and oil changes were the only expenditures (aside from wants) from new until last year.
How do you know it never had one misfire.. Do you carry a live data comp with you as I do? If not, I would lay odds you have had more misfires then you are aware of..
And yours certainly does NOT look beat to death.. It looks great!
It got the best care money could buy...I only meant that I never had any part failures, such as water pumps, front end parts, drive train parts ETC..
Tires, brake and oil changes were the only expenditures (aside from wants) from new until last year.
How do you know it never had one misfire.. Do you carry a live data comp with you as I do? If not, I would lay odds you have had more misfires then you are aware of..
And yours certainly does NOT look beat to death.. It looks great!
tjkj2002
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Never had a misfire code.Every engine,yes that means just like stated, has misfires but 99% of the time they are not felt and not frequent enough to cause any issues.What can seem like a misfire maynot even be a misfire,more so in a 3.7 with a balance shaft.
Look at a top fuel dragster engine,over 25% of the 1/4 mile(now 1000') trip it's misfiring since the plugs are melted.
Searcher67
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Just perusing over my receipts :
2 nd set of tires (unless you count the 4 months of Goodyear craps that came with it, then it would be 3)
3rd set of front brakes
2 nd set of rear brakes
2nd windshield
3rd radiator (Damn plastic crap)
a multitude of wipers, alignments, oil changes, spark plugs an
Aside from that and up until last spring nothing else had ever failed on the Libby, which is why it rates so high with me..
Granted mine had never seen much more then rock strewn trails, ocean beaches and mt trails.
Seriously, there are problems with the new JK's.. ?
2 nd set of tires (unless you count the 4 months of Goodyear craps that came with it, then it would be 3)
3rd set of front brakes
2 nd set of rear brakes
2nd windshield
3rd radiator (Damn plastic crap)
a multitude of wipers, alignments, oil changes, spark plugs an
Aside from that and up until last spring nothing else had ever failed on the Libby, which is why it rates so high with me..
Granted mine had never seen much more then rock strewn trails, ocean beaches and mt trails.
Seriously, there are problems with the new JK's.. ?
Searcher67
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Yeah, unless I'm looking at the live data, most times I don't feel the misfires and only once did it ever throw the multi misfire code which led to a MIL illumination. That was right after the head gasket went the first time.
Which is another reason I have disconnected the computer. I get tired of seeing what I cannot feel... I tend to have a touch of OCD when it comes to my vehicles!
Which is another reason I have disconnected the computer. I get tired of seeing what I cannot feel... I tend to have a touch of OCD when it comes to my vehicles!
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