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  1. #1
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    Smile Can't find this engine miss, help...

    I just posted these videos on YouTube of my XJ idling cold and then warm:

    1. [ame="http://www.youtube.com/watch?v=mrVtCL6nQh4"]1999 Jeep XJ - Rough Idle Misfire at Idle - Video 1 - YouTube[/ame]

    2. [ame="http://www.youtube.com/watch?v=X5FRFsGpuTo&feature=mfu_in_order&list=UL"]1999 Jeep XJ - Rough Idle Misfire at Idle - Video 2 - YouTube[/ame]

    I've got a new pre-cat NTK O2 sensor installed yesterday.
    4-pin hole fuel injectors - can hear them firing fine with listening tool (http://www.fiveomotorsport.com/ for stock XJ)
    fuel pump module - good pressure on rail Bosch
    IAC sensor - replaced Autozone
    CPS - replaced Autozone
    newer plugs/wires/cap/rotor Champion/Delphi/Brass connections
    newer coil - Accel
    IAT sensor - replaced Autozone
    TPS - replaced Autozone
    MAP sensor - replaced Autozone
    clean engine oil
    all fuses look good
    tested lots of circuits with volt meter - found nothing

    Ordered a new Coolant Temperature Sensor last night OEM

  2. #2
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    Default Re: Welcome jbossnack!!!

    Hey what do you see from the tailpipe when it's missing? Any water vapor (steam)?

  3. #3
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    Icon6 Re: Can't find this engine miss, help...

    Is there any chance your gasoline is not that good?...xjtalk
    PVT. Tadpol XJ

  4. #4
    denverd1's Avatar
    denverd1 is offline Level: Uber Jeep Cherokee Trailer Queen
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    Default Re: Can't find this engine miss, help...

    mine didn't have a tailpipe for a while. got one put on for inspection. started hearing the same miss. Although i didn't hear it last time I took it out......
    Wheelin' East Texas in a RED XJ

    RED 98 XJ with 4.5" lift, ZJ steering, front and rear locked on 33's
    cowl intake, Cobra CB, SYE, bumpers, 10K winch, lights
    ,___________
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  5. #5
    LizardRunner's Avatar
    LizardRunner is offline Level: Uber Jeep Cherokee Trailer Queen
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    Default Re: Can't find this engine miss, help...

    Just to be sure, try doing the paper against the tail pipe test. if it sucks in any at all you have a valve issue. It could also be a valve seal issue since it happens more when fully warmed up. with these out of the way, check for the vapor Muddy mentioned and one other thing I can think of that's out of the norm would be a vacuume leak somewhere.
    2004 4.7v8HO WJ OMG, it's RED , Green bits are now under the hood. Loving the F/R Lockers and D44's. RIP 2011 Lil Ric and Gordo. RIP 2012 Jessie RIP 2013 Kat. RIP 2013 Ed . Lizards can always climb but sometimes they loose their tails to get away. The true patriot will stand beside the soldier when the time comes to fight Now building Asnikiye heca (Buzzard's Roost) homestead farm. My road is my wheeling trail

  6. #6
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    Default Re: Can't find this engine miss, help...

    There is a good steady stream of exhaust gas coming out of the tail pipe. It will not suck up the paper so I think the valves are just fine.

    There is a lot of moisture coming out the back of the tailpipe. Maybe it's the weather (kinda of humid) but there is a lot of condensation. I think that's good though.

    The gas is fine, new, same as in other vehicles I'm using. No problems with them.

    I really think this is some sort of 1) vacuum leak or 2) bad sensor

    I have checked for vacuum leaks everywhere except for the that thing located in the front bumper passenger side. It's a round ball canister.

    Another guy on YouTube says it's the CPS and I need to buy MOPAR only. I have an Autozone CPS, he says they are crap, but I'm not sold on his opinion.

  7. #7
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    Default Re: Can't find this engine miss, help...

    Quote Originally Posted by jbossnack View Post
    There is a good steady stream of exhaust gas coming out of the tail pipe. It will not suck up the paper so I think the valves are just fine.

    There is a lot of moisture coming out the back of the tailpipe. Maybe it's the weather (kinda of humid) but there is a lot of condensation. I think that's good though.

    The gas is fine, new, same as in other vehicles I'm using. No problems with them.

    I really think this is some sort of 1) vacuum leak or 2) bad sensor

    I have checked for vacuum leaks everywhere except for the that thing located in the front bumper passenger side. It's a round ball canister.

    Another guy on YouTube says it's the CPS and I need to buy MOPAR only. I have an Autozone CPS, he says they are crap, but I'm not sold on his opinion.
    There is a know issue where the harness rests and rubs on the fuel rail near the firewall. Check to see if the harness is resting on the fuel rail. Just use a tie wrap to pull it up and off the rail. The rail rubs through the installation of the "right" wire and randomly grounds it. Probably would manifest as a miss, but have a look anyway.

  8. #8
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    Default Re: Can't find this engine miss, help...

    Was this issue ever resolved ?

  9. #9
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    Default Re: Can't find this engine miss, help...

    That surging idle is a classic symptom of a TPS problem. You've recently changed the TPS so it's unlikely that the sensor itself is at fault, but it's not uncommon for the wiring harness connector to the TPS to deteriorate with age and malfunction. Try wiggling the wires to that connector and the connector itself to see if that makes the idle worse (or better). If it does, you've found the problem.
    A vacuum leak will usually cause a steady high idle on a speed density EFI engine like the Jeep 4.0 rather than an erratic idle, and a bad CPS usually causes stalling/starting problems.

    1992 XJ - 4.6L Stroker - AX15 - Sold 13/12/2016
    202rwhp 258rwtq (248bhp 311lbft crank)
    Jeep Performance, Jeep Tech, Junker to Stroker

  10. #10
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    Default Re: Can't find this engine miss, help...

    im glad you made this post jbossnack! Im having the same exact problem! but i have a 2000 jeep cherokee. im about to do a fuel pressure test on it now and see if the fuel pump because when i turn the key it takes a minute to fire up. but im also going to check out what Mudderoy and Cheromaniac is saying, they gave so good information! Thanks guys!
    6.5'' Rough Country lift, 35x12.5x15 BFGoodrich M/T's, 15'' Cragars Beadlocks, Rusty's TBS, A.A. SYE, Optima (red top) Battery, CB Radio w/5'' Fire Stick Antenna, Flowmaster Super 44 Dual Custom Exaust, 4 Cheep 2'' Bumper Lights, Custom Front bumper /w Stinger, Yakama Bike Rack, Garmin GPS, Kenwood 6.5'' Indash Radio, 4 6.5'' Kenwood Speakers, 12' Alpine Type R Sub In Custom Jeep Enclosure, Alpine mono Amp, Ect.

  11. #11
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    Default Re: Can't find this engine miss, help...

    Quote Originally Posted by modestmar00xj View Post
    I'm having the same exact problem! but i have a 2000 jeep cherokee. im about to do a fuel pressure test on it now and see if the fuel pump because when i turn the key it takes a minute to fire up.
    Your problem is different and this might be the reason behind it:

    http://www.wjjeeps.com/tsb/tsb_wj_1400201.pdf

    Although that TSB is for the '99-'01 WJ, it's also relevant to the XJ.

    1992 XJ - 4.6L Stroker - AX15 - Sold 13/12/2016
    202rwhp 258rwtq (248bhp 311lbft crank)
    Jeep Performance, Jeep Tech, Junker to Stroker

  12. #12
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    Default Re: Can't find this engine miss, help...

    Again I ask, was this issue ever resolved ?

    Thanks,3

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