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4.0 Bad idle please help

Discussion in 'Cherokee' started by Rkarr22, Sep 21, 2019.

  1. Sep 21, 2019 at 11:12 AM
    #1
    Rkarr22

    Rkarr22 [OP] Member

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    Let me start out by saying I'm new here and really appreciate any and all support you have to offer.

    So long story short, I got a 95 ZJ decided the throttle body needed cleaning, put it back on and boom bad idle. I've changed the idle air control valve 3 time and the pressure sensor to no avail. The Haynes manual said it's the computer but Haynes has told me that before and been wrong

    Here is a link, sound is bad but the idle goes up and down from about 600 rpm to 1200 until I pull ether the air control or pressure sensor. Pulling the pressure sensor gives better results.

    https://youtu.be/u1Q31xr_grg

    V/R
    Ryan
     
  2. Sep 21, 2019 at 11:30 AM
    #2
    Awrench

    Awrench Well-Known Member

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    bad idle 1st suspect is IAC, you replaced the IAC motor, did you clean the ports- the passage ways in the throttle body?

    second you are unplugging the MAP sensor electrical connector, with engine running is there vacuum on the rubber tube/hose going to sensor?

    As you have removed the 2 wire connectors (IAC, MAP) you SHOULD have a CEL light on - yes or NO?

    Might want to check codes, a 1995 is OBD1, not a great system but don't know till we look. Post all codes.
     
    JKBob 25 and Bob like this.
  3. Sep 21, 2019 at 1:06 PM
    #3
    Rkarr22

    Rkarr22 [OP] Member

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    I did clean the ports with degreeser, metal brush and brake cleaner.

    There is vacuum through all hoses coming off the the intake manifold including to the MAP.

    I have a code. 12 & 22. 12 is battery power to PCM was disconnected. And 22 ECT voltage too low/too high. FYI: I've also change the ECT

    Sorry don't have an OBD1 right now.
     
  4. Sep 21, 2019 at 2:03 PM
    #4
    Awrench

    Awrench Well-Known Member

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    unplug the ECT sensor, probe the wires, BK/LB should be 5v and the other wire - TN/BK no voltage...

    let me know...
     
  5. Sep 22, 2019 at 9:59 AM
    #5
    Rkarr22

    Rkarr22 [OP] Member

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    So the ETC is coming up with 4.9. It holds for a few seconds will drop to any number between 4.2 and 4.8

    I'm really new to this and don't know what TN/BK means. I grounder my tester and probed each terminal.
     
  6. Sep 22, 2019 at 10:12 AM
    #6
    Awrench

    Awrench Well-Known Member

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    TMI -
    TN/BK is the wire colors - meaning Tan with a Black tracer/stripe.
    Those colors tend to fade and 'change' BUT there will clearly be a difference between the 2, tan could be cream, gray, might need 'imagination' to sort out.

    the 4.8 to 5.0 volt is fine, was there any voltage on other wire? was it grounded?
    Anyway right now I would back burner the code issue.
     
    Rkarr22 [OP] likes this.
  7. Sep 22, 2019 at 12:27 PM
    #7
    Rkarr22

    Rkarr22 [OP] Member

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    Black with light blue is grounded. Tan has 5v. No voltage to black
     
  8. Oct 4, 2019 at 9:20 PM
    #8
    Rkarr22

    Rkarr22 [OP] Member

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    So I changed the temperature sensor, for the 2nd time and still had idle issues. Are we looking at a computer problem now?
     
  9. Oct 5, 2019 at 5:29 AM
    #9
    Awrench

    Awrench Well-Known Member

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    lets hold off on condemning the PCM.
    So all was running OK when all this idle issue started?
    You removed cleaned the IAC then replaced the IAC.
    NOW the idle varies @600-1200 RPM, Claim removing ELEC connector to IAC or MAP idle corrects to what?

    Sounds like the PCM is trying to control the idle (good) but GIGO, likely a bad input confusing PCM.
    If applicable is the airbag light on? Does airbag bulb come on every start?
    With bad idle unplug TPS - did it smooth out like unplugging IAC and MAP?
     
  10. Oct 5, 2019 at 6:43 PM
    #10
    Rkarr22

    Rkarr22 [OP] Member

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    All was ok then I cleaned the throttle body. After that bed idle. Replaced 2 new IAC, no chang. When unplugging the IAC idle is about 600 with slight fluctuations. Unplugging the TSP idle is 1100 with no fluctuations.

    The airbag light is on on every start.

    When I unplug the TPS it still has a bad idle.
     
    Last edited: Oct 6, 2019
  11. Oct 12, 2019 at 12:38 PM
    #11
    Rkarr22

    Rkarr22 [OP] Member

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    Oh, resolution was a bad pigtail going to the TPS.
     
    aggrex likes this.
  12. Oct 12, 2019 at 5:40 PM
    #12
    aggrex

    aggrex Well-Known Member

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    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Always feels good to have some positive resolution
     
    Rkarr22 [OP] likes this.
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