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Thread: Uncontrolled acceleration!

  1. #11
    Join Date
    Jan 1970
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    NSW SW Slopes
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    The wires to the EGR throttle butterfly motor are intercepted so that the butterfly motor can be powered, isolated from the ecm supply, for 15 seconds after the ignition is switched off although aborted if the ignition is switched back on. A double pole relay ensures no feed-back to the ecm. The wires can be readily intercepted near the throttle housing on the 2.7/3.0 but not so readily on the 4.4 so mine were intercepted at the ecm plug. Ignition and permanent 12V power via a fuse plus earth are also required.

    The EGR butterfly is normally used to deprive the engine of fresh air to increase recirculated exhaust gases though the engine to decrease oxygen content. One of the European car manufacturers, which IIRC is Audi, added the closing of their EGR throttle butterfly on their diesel V8 on engine shut-down to rid the engine of compression roughness in the final second or 2, a smoothness that I immediately noticed on my 4.4 TDV8.

    It appears from DTCs (fault codes) for the 3.6 TDV8 that the 3.6 TDV8 ecm will do the same trick if it detects uncontrolled engine operation but no equivalent DTCs exist for the 2.7, 3.0 or 4.4 engines which have all suffered self-destruction from runaway.
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

  2. #12
    Join Date
    Aug 2012
    Location
    Greenvale, Melbourne
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    I went CSI with matts.
    There are 2 floor mats in this car, a loose rubber matt on top of a pinned carpet one. I could not see those how matts can interfere with the pedal mechanics though.
    I tried moving the rubber matt with my feet, it requires considerable and purposeful effort to slide the matt forward and there is no way it would slide on top of the pedal. I also placed the rubber matt on top pedals but but again it would not have enough weight to keep pedal pressed and go unnoticed by the driver.
    IMO it was not the cause.
    I am hoping the LR mechanic would come up with plausible explanation and definite fix otherwise this car is not safe to drive, out of warranty and not sure what would be the next steps...

    Attachment 153477

  3. #13
    Join Date
    Jan 1970
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    NSW SW Slopes
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    Did your wife get the feeling that the accelerator pedal was actually stuck down or was that an assumption from the continued acceleration?
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

  4. #14
    Join Date
    Aug 2012
    Location
    Greenvale, Melbourne
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    Hi Graeme,
    She is sure that the pedal was down and later on she also felt it got released with little thump.
    We are still debating what might have worked at the end and she now thinks she pulled the park brake.
    Thnx

  5. #15
    DiscoMick Guest
    She probably didn't think of it while panicking, but would moving the gear selector into neutral have been possible or would it have refused to shift because the engine was racing?

  6. #16
    Join Date
    Jan 1970
    Location
    NSW SW Slopes
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    There is no difficulty in shifting to neutral under load.

    My L322's throttle pedal assembly is operated by an almost vertical rod passing through a rubber grommet, but there is a considerable gap down which a small stick or stone could fall that might jam the mechanism. My L322 is 4 years older but I don't know if the gap has recently opened-up or if it has existed for some time.
    If it is possible that the pedal jammed then it should be opened and checked or replaced.

    Edit: Your accelerator pedal is suspended from above so not at all like my L322.
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

  7. #17
    Join Date
    Aug 2012
    Location
    Greenvale, Melbourne
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    Just an update,
    The worst has happened, after in and out of mechanic for various readings and tests, the results is inconclusive.
    Simply cannot replicate the problem or determine the cause.
    We will continue to monitor...
    Thnx

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