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Thread: Broken cruise control

  1. #1
    Join Date
    Apr 2018
    Location
    Essex, UK
    Posts
    31
    My Cars
    '95 840Ci, '06 730d

    Broken cruise control

    So for no apparent reason, the once perfectly functioning cruise control on my 840 decided to pack up on Friday.

    Now, if I push forward on the stalk to set the speed and release the throttle pedal, the revs and road speed drop. The stalk has no effect when pushing forward to increase the speed. Interestingly, if I reapply gentle pressure to the throttle pedal to maintain he road speed, the cruise control does seem to kick in and hold the speed for a couple of seconds.... but then, alarmingly, the speed will continue to rise above the speed I’d set with the stalk. It continues to rise until the brake pedal is pressed - pressing up or down on the stalk to cancel the cruise control doesn’t work.

    Any ideas? I’ve cleaned the electrical connections on the actuator under the hood, lubed the spring mechanism on the throttle body and checked the cable moves freely. Do the control modules in the trunk ever go bad?
    Last edited by Dan840ci; 06-17-2018 at 05:46 AM.

  2. #2
    Join Date
    Jul 2002
    Location
    AZ & CO
    Posts
    980
    My Cars
    Too many ;-)
    Subscribed to this thread as my CC only works sporadically too. Not exactly the same symptoms, but similar....
    "Asphalt is evil, it must be punished!"
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  3. #3
    Join Date
    Feb 2010
    Location
    Hampshire UK
    Posts
    8,867
    My Cars
    99 840ci Sport Indv
    The actuator motor has failed by the sound of it - these were used in a few models so you can find them on Ebay pretty cheaply....

    More info here:

    http://www.meeknet.co.uk/e32/BMWCrui...hnicalData.pdf
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  4. #4
    Join Date
    Apr 2018
    Location
    Essex, UK
    Posts
    31
    My Cars
    '95 840Ci, '06 730d

    Broken cruise control

    Quick update on this, and some advice for anyone else attempting it...

    I bought a used cruise actuator from a breakers in Germany, £60 all in. It was from an E34 so the cable had to be changed over. removal of the cable was straightforward on the bench, but the existing cable needed the engine cover to be removed so that I could unhook the end from the throttle body to allow enough slack to pull the other end out from the existing actuator. Anyway, I did that, swapped it over and went for a test drive. Which is where things went a bit wrong....

    Got to a clear stretch of residential road, got it up to 30mph and set the speed. It held, but the speed kept rising. Cancelled the cruise via the stalk, speed kept rising. Pressed the brake pedal, speed levelled off but revs keep rising slowly. “Not good”, I thought to myself.

    Tried shifting into Neutral, revs shot up to the red line with the engine no longer hindered by the gearbox. Only thing I could do was turn the engine off at the key and brake to a stop. Anyway, turns out the linkage at the throttle body had jammed open when the cruise cable pulled it back (when I set it with the stalk). I suspect this was because there was a kink in the steel cable inside the plastic sheath, caused by the right angle bend. When I’ve disturbed the cruise cable by unhooking it from the throttle linkage, I’ve neglected to take up the slack by twisting the threaded collar. When the cruise kicked in the kinked cable must’ve gone too far back into the sheath, past the right angle and then just stuck there, holding the throttle open.

    Not a pleasant experience, but no lasting damage.

    Almost forgot - big thanks to Timm, as always, for pointing me in the right direction.
    Last edited by Dan840ci; 06-28-2018 at 04:53 PM.

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