Cherokee XJ 4.0 Misfire Gremlin .....





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  1. #1
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    Default XJ 4.0 Misfire Gremlin .....

    A while ago my XJ started having the ocasional slight misfire .... just a slight puff .... puff .... only when the engine gets to normal running temperature.
    Like a plug that misbehaving.

    So I changed the plugs, correctly gapped etc.
    Problem went away ..... just to come back about a month later.
    Suspected that one of the new plugs was playing up ....
    So bought another two new plugs, and no in the process of systematically replacing then again ... in the hope to find one that is misbehaving.

    On every change, problem goes away for a few days and then comes back again .... very frustrating.
    Engine runs like a dream otherwise.

    All wires and vacuum pipes are OK.
    No apparent loss of power
    No strange noises
    No smoke
    No heat or oil pressure problems
    No sign of spark getting thrown away around the distributor caps and plug leads when checked in pitch black conditions

    So what can it be ?
    Ignition Coil ? How can I prove it ? Cost ?
    O2 sensor ? How can I prove it ? Cost ?

    Please help if you can .....I see $$$$$ everywhere again.

    This is my daily ride, so I need to get to the bottom of it.
    Last edited by Johann van Rensburg; 2014/11/16 at 07:02 PM. Reason: Fixed formattting

  2. #2
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    Default XJ 4.0 Misfire Gremlin .....

    Fixed formatting
    Last edited by Johann van Rensburg; 2014/11/16 at 07:02 PM. Reason: Fixed formatting

  3. #3
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    Sorry about the messy format guys .... my editor does not want me to format differently ... neater.

  4. #4
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    Check that the throttle body is clean. It's an easy-enough execise. Just unclip all the throttle cables, unclip the 3 electrical plugs, undo the foor bolts and lift the whole throttle body off. Clean it with some carb cleaner, and refit.

    Take care not to push the piston on the IAC on the throttle body.

    Next check all the electric plugs, and clean them with some contact cleaner spray.

    Alsoo unclip the plugs that go into the ECU, clean them with contact spray and refit them.

    I'd do this long before I even look at the O2 sensors.
    Work. It's a wealthy man's privilege, and a poor man' fate....

    André Opperman


    "Boerbok" - 98 Jeep XJ 4lit auto
    "Gloria" - 04 Ranger D/C 4lit auto

  5. #5
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    Thanks Andre ... I will be doing all that tomorrow.Just received a quote from teh dealers on parts:O2 sensor R1100Coil R500Dist Cap R300Plug leads R950At least a lot less than I expected.

  6. #6
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    Quote Originally Posted by Johann van Rensburg View Post
    Thanks Andre ... I will be doing all that tomorrow.Just received a quote from teh dealers on parts:O2 sensor R1100Coil R500Dist Cap R300Plug leads R950At least a lot less than I expected.

    Yip Johann, and if you believe the Toy boys out there Jeeps are way more expensive than Toys for parts. Not true.

    In your shoes, I would also see if I can get a fellow XJ'er to help you. Park the XJ's next to each other and swop out parts 'till you get the problem to transfer to the other XJ. Not always so easy, but it potentially saves a lot of time and unnecessary expense.
    Work. It's a wealthy man's privilege, and a poor man' fate....

    André Opperman


    "Boerbok" - 98 Jeep XJ 4lit auto
    "Gloria" - 04 Ranger D/C 4lit auto

  7. #7
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    Had lots of fun on my ex XJ:

    Model: Cherokee XJ 4.0
    Year: 1997
    Mileage: 305500km
    Problem: Exact same issue as I had Dec 2009 at 291k km -> Inconsistant idling +-2 min after startup (hot or cold), give it a rev (or leave for a minute) and it idles smoothly. During this same time pulling away at light throttle resulted in jerky acceleration
    Cause of problem(if known): Oxygen sensor had given up the ghost due to the previously faulty injectors.
    Specifics of repair work carried out: Replaced Oxygen sensor
    Cost of repair: R1k
    Who did the repair: Parts from Jeep, work carried out by myself
    Vehicle under warranty, Y/N: N
    Was damage covered by warranty: N/A

    Model: Cherokee XJ 4.0
    Year: 1997
    Mileage: 303000km
    Problem: The Jeep started missfiring the other day and cutting out when coming to a stop at a robot, reving it above 2000rpm no problem (made for an interesting drive back home in the traffic). The scanner showed an error code p0351 (coil). Found a loose earth connection right below the coil and fixed this. Drove fine for a day or two and then started cutting out again, made it halfway home before it finally refused to start. Scanned it again and again had the p0351 and also a new p0108 error code. Cleared the codes and still it refused to start. Removed the coil and before temporarily fitting it to DeonXJ's Jeep I accidentily dropped it. Worked fine in Deon's Jeep. Plugged back in mine and the Jeep started prefectly. Got out the rubber mallet and gave the coil a couple of hits, every hit would see it either splatter or die. Thus coil positively identified as culprit.
    Cause of problem(if known): Coil broken
    Specifics of repair work carried out: Fixed earth problem and fitted a new coil
    Cost of repair: R400
    Who did the repair: Myself
    Vehicle under warranty, Y/N: N
    Was damage covered by warranty: N/A

    Note after this incident I also replaced the distributor cap and rotor which solved the issue
    '99 Cherokee (XJ) 4.0 @ 143000km
    "Frankenstein" 5" lift | Nomad Bumpers | Safari Snorkel | Gorman rocksliders | Khumo 31x10.5x15 | Jerry can holders | 29Mhz Radio | Custom roof rack | Dual Battery | ARB onboard compressor

  8. #8
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    Ha hA

    Maybe I need to just buy a second same model XJ .....

    Yeah, getting a local to agree to part swopping would be almost impossible.
    The misconception about expensive parts does not help at all ... just makes it worse.

    At least I am able to do any of the labour myself - kitted and qualified ... so that saves a lot.

    I LOVE my XJ ...
    Last edited by Johann van Rensburg; 2014/11/16 at 07:03 PM. Reason: Formatting

  9. #9
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    Thanks Sclater

    I actually read about your experiences earlier this week, and they were the lead up to some of the questions in my post.

    Very helpful as always ....I think I need to move to Capetown .... much more XJ support there ....hehehehe
    Last edited by Johann van Rensburg; 2014/11/16 at 07:04 PM. Reason: Formatting

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    Quote Originally Posted by Johann van Rensburg View Post
    Thanks SclaterI actually read about your experiences earlier this week, and they were the lead up to some of the questions in my post.Very helpful as always ....I think I need to move to Capetown .... much more XJ support there ....hehehehe

    While it's a brilliant reason to move down, it's by no means the best one!

    Just do it, we need more XJ'ers here...

    Work. It's a wealthy man's privilege, and a poor man' fate....

    André Opperman


    "Boerbok" - 98 Jeep XJ 4lit auto
    "Gloria" - 04 Ranger D/C 4lit auto

  11. #11
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    Quote Originally Posted by Oppers View Post
    While it's a brilliant reason to move down, it's by no means the best one!

    Just do it, we need more XJ'ers here...

    Agreed André. Plenty of helpful people here
    Barnie Hickman
    Jeep XJ 95 "Witblitz" Jeep XJ 99 "Goldi" Swambo's

  12. #12
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    Before you spend any money check for codes.

  13. #13
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    Thx for the helpful feedback guys.

    Now we have to wait and see...

    Cleaned the throttle body .... was seriously gunged up on the IAC side.

    For now the miss appears to be gone, but will have to wait and pray it stays away.

    @ XJ Junkie ..... even checking for codes will cost money I suppose .... I do not have a scan tool.
    Built in diagnostics give code 55 ... all clear.
    What else can it be .... other than the O2 sensor ?

    Question, as a matter of interest .... where does your oil pressure gauge normally sit when up to running temp ? ... Just curious.

  14. #14
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    You can check this way http://youtu.be/HL8xYrIPaQU

    From experience, your problem is usually always the crank sensor. Your symptoms were the same as what I had. It's about R1500 for a new one. 5 mins to fit.

    Edit: as far as the oil pressure goes, it fluctuates.

  15. #15
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    Quote Originally Posted by Oppers View Post
    .....

    Take care not to push the piston on the IAC on the throttle body.

    ......
    Managed to not disturb it by cleaning very carefully around it .... thick gunge all round ....

    Once I got the gunge to be pretty soft I needed to remove the whole thing with the piston not moving, so that I could clean all the areas thoroughly .... too best part of an hour just doing this.

    Sounded like it re-adjusted itself anyways when I started up again .... idle went high for about a minute and then started dropping back to normal.

  16. #16
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    Thx XJ Junkie ....

    That's what I did .... mine is 96 model .... engine check light flashes need to be counted to get the code .... in my case "55" .... all clear.

    How recent is that price ?

  17. #17
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    Price is what I payed at an Indy maybe 2 years ago.

    The misfire evident in this video was evident after I changed the plugs & coil pack. It was better but not fixed. The crank sensor resolved the problem for good

    http://youtu.be/DnI4-2iVhds

  18. #18
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    OK .... update .....

    Maybe I should now call this a "rough idle" .... eish.

    It is definitely progressively getting worse ....

    Where to now ?

    O2 sensor or Crank Position sensor ?

  19. #19
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    Is it ok when cold, then gets worse?

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    Yes ...seems like it ..
    Also does smell a bit "rich" when the problem starts.

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