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Thread: Stumped on intermittent idle problem

  1. #1
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    497

    Default Stumped on intermittent idle problem

    Every 10-20 starts or so the Jeep fires up very roughly. It never happens cold, and usually after a 5-15 minute stop for an errand. Runs really rough for a minute or two, and does not respond to tapping the pedal.

    IAC valve has been removed and cleaned.
    Connection to IAC has been cleaned with electric cleaner.
    New plugs.
    Intake cleaned.
    Two instances of check engine light from this behavior: #3 misfire, and then a generic misfire code later.
    Dealer sucked a can of M44 top end cleaner through the system.
    Have run a bottle of Lucas with each tank since.

    Running out of trial and error money right now so I'm hoping one of you folks has some experience to share. My wife won't drive it until this is resolved and she's missing what I traded for the Jeep over this as well.

    Thanks for the help.
    Last edited by packmule1911; 12-28-2014 at 04:36 PM.

  2. #2
    Join Date
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    Durham NC
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    Default Re: Stumped on intermittent idle problem

    Forgot to add: yesterday when this happened, I tried tapping the pedal anyway, and I got a couple of tiny popping "backfire" sounds from the engine bay. At least they didn't sound like they were from the back end.

  3. #3
    Join Date
    Sep 2009
    Location
    Chico, CA
    Posts
    29,847

    Default Re: Stumped on intermittent idle problem

    Might check that throttle position sensor. Any codes or CEL?
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  4. #4
    Join Date
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    Location
    Durham NC
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    497

    Default Re: Stumped on intermittent idle problem

    I don't know that part, but I'll be learning I guess.

    I don't recall the code numbers but the first check engine code was for cylinder 3 misfire, and the second was a general misfire.

    Don't know what a CEL is. More to learn.

  5. #5
    Join Date
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    Location
    Durham NC
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    497

    Default Re: Stumped on intermittent idle problem

    A TPS isn't expensive. Any particulars around installing it?

    I read an article on testing a TPS with a multimeter. I have one, but electrical stuff is not my strong suit.

  6. #6
    Join Date
    Sep 2009
    Location
    Chico, CA
    Posts
    29,847

    Default Re: Stumped on intermittent idle problem

    Well, CEL is shorthand for check engine light. Got one on?
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  7. #7
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    497

    Default Re: Stumped on intermittent idle problem

    Duh. Sorry.

    Yea, the light has been on twice. Cylinder 3 misfire was the code the first time, and a general misfire the second time.

    The CEL did not come in from the occurrence yesterday and remains off now.

  8. #8
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    Sep 2009
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    Chico, CA
    Posts
    29,847

    Default Re: Stumped on intermittent idle problem

    Not having a CEL makes it a little tougher. One more question or two. How long since the upstream O2 sensors have been changed?
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  9. #9
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    497

    Default Re: Stumped on intermittent idle problem

    I've had it a month and never changed any 02 sensors.

    When it starts this way, if I set there and let it idle a few minutes it smoothes out just fine. When it starts right, which is most of the time, it runs really well at 750 rpm idle. Maybe some slight fluctuations, but slight.

  10. #10
    Join Date
    Sep 2009
    Location
    Chico, CA
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    Default Re: Stumped on intermittent idle problem

    Since it straightens itself out when warm, I think at this point that you either have a temp sensor problem, which I think is very slight. I think that there might be a slight TPS problem, but the main thing at this point is probably the O2 sensors, which no one ever changes until they fail completely
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  11. #11
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    497

    Default Re: Stumped on intermittent idle problem

    It only does this when it's warm, but straightens itself out after a few minutes idling when it does this. It's never done this when cold.

    What does a completely failed 02 sensor act like.

  12. #12
    Join Date
    Sep 2009
    Location
    Chico, CA
    Posts
    29,847

    Default Re: Stumped on intermittent idle problem

    Runs rough, stalls or horrible gas milage
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  13. #13
    Join Date
    Dec 2014
    Location
    Durham NC
    Posts
    497

    Default Re: Stumped on intermittent idle problem

    Looks like the issue is the "heat soak" problem:

    TSB 1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
    Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
    Model Year(s): 1999-2004

    Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

    Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

    This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

    If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

    Parts required:
    56028371AA Ignition Wire Shield

    Repair procedure:
    1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
    2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
    3. Confirm sleeve is flush to intake manifold surface around injector.
    4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position.

  14. #14
    Join Date
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    Location
    Durham NC
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    Default Re: Stumped on intermittent idle problem

    OK Folks.

    If I've got insulation on top of the intake manifold, and heat resistant tubing about the number 3 injector (per the TSB), and I still get some heat soak problem behavior, what's left to try? Do new injectors work as an ultimate fix for this issue?

    If injectors will work, do credible reconditioned ones work ok? I understand that there are upgrades to be done with the injectors (Neon, Ford, etc.), but which do folks like the best? I like the reconditioned price.

  15. #15
    Join Date
    Oct 2011
    Location
    S.E. Texas
    Posts
    29,260

    Default Re: Stumped on intermittent idle problem

    I've heard of people using heat shielding on the underside of the intake manifold to keep radiated heat from the exhaust manifold/header down some. Although, it would be next to impossible to install it with the intake installed.

    Sent via messenger pigeon - i talk, he types.

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