pesky p0300 random misfire issue--- FIXED!!!!

Discussion in 'KJ General Discussion' started by Central NY guy, Jun 26, 2014.

  1. Central NY guy

    Central NY guy New Member

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    This is my first post here but I've read a lot the past couple of years and gathered a bunch of information.

    I own a 2003 Liberty sport with the 3.7. My sister bought it in 2007 and around 2009 up came p0300 and then misfire code for each cylinder soon followed. She took it a dealer where she was told "needs valve job, will cost around $5000". Her and my brother in law said no to that and took it to a local mechanic who threw part after part after part at it with NO success. they just kept driving it with the engine light on. Inspection for 2010 was due and back to the mechanic they went. After close to $500 in parts thrown at it and having it a month he got it to pass inspection. Called my sister and said "good news is you have an inspection sticker, the bad news is that the light is back on"

    Inspection for 2011 went the EXACT same way! My sister was sick of the Liberty and wanted to be out from under it. I did a lot of searching and told myself "I can fix this." I bought it the end of June 2012 for $3000 with 74,xxx miles. My 2 year registration is to renewed the end of this month and for the FIRST time during the time my sister and I both owned it it's good to go.

    That's how I acquired the Liberty. Over the winter 2012-2013 I bought some remanufactured heads and replaced because a friend who works for.chrysler told me about the valve seats getting out of round and causing issues. He told me what I would see if they were damaged.... sure enough. So I did the head job (about $1000 total for parts) and around 100 miles later.... back come the codes.

    Didn't go any further at that time with the misfiring because I left the bar one.night and decided to park it.in a ditch. Time for scrapyard engine cradle and LCAs.

    I have driven this jeep HARD!! Welded spider gears and I slap old tires on for burnouts, beat on her offroad, etc... Everyone with cherokees around here are impressed what the Liberty will do offroad.

    So anyways I talked with old guy near me who's always been a gearhead and he told me "crank sensor" okay in goes crank sensor... NOTHING!! oh well only out $37.

    Then a nice rotten egg smell from exhaust, I cut out the big cat (no sensors around it) and installed pipe in it's place. No more smell so might be lucky and mini-cats are okay for now. FINALLY decided to buy myself software to turn laptop into a code reader/scanner. It checks readiness monitors, a crap load of PIDs, freeze frame data (kicks out data when you run out of fuel lol), and even brings up mode $06 data. Doesn't tell me what each thing is but at least I get the numbers. 4 of the 21 sensors (and whatever else it reads) are failed. All four of them below minimum values. Called my friend at Chrysler and he said that they are the o2 sensors. I replaced all four of them. Cleared codes, drove it about 60 miles and all 7 readiness monitors are completed, and all 21 sensors,etc.... under mode $06 have passed. I got it inspected and it's now been around 2000 miles with no engine light and scanner shows NO pending codes.

    I apologize for the long post but.figured I would make my first one worthwhile. I did learn a great deal about.this thing from this forum and I hope to learn more, and help others if.I can
     
  2. dude1116

    dude1116 Full Access Member

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    1) Sounds like you had a good night at the bar. Glad nobody was hurt...

    2) We probably could have told you that from the start...! Always a good idea to start cheap, then go more expensive/complicated.
     
  3. mu2bdriver

    mu2bdriver Full Access Member

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    Nice work. I had the same issue with an o2 code and a new sensor fixed both. People on other sites were convinced it was a bad cat converter but this site taught me otherwise.
     
  4. Dave

    Dave Administrator Administrator Moderator

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    Glad that you got it fixed and welcome to the forum.


    Dave