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Sticky throttle pedal

Discussion in 'E30 (1984-1993)' started by az3579, Oct 25, 2008.

    • Member

    az3579

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    Sorry, I copied and pasted my other thread on Bimmerforums:

    Does anyone have a choppy throttle pedal? Mine is so bad that there is no "ease on the gas". My throttle has two modes: On or Off.

    I drove someone else's E30 today and maaaaan was it so smoooooooth. I could see myself driving my car absolutely perfectly with no head banging at every shift if my pedal was that smooth.



    Would anyone know what would cause this? I'm very suspicious of my accelerator tension spring as shown here, item # 12:
    http://www.realoem.com/bmw/showparts...23&hg=35&fg=10

    I WD40'd the hell out of it and it helps a very small amount, but is still choppy at first and gets just as bad in a few minutes as it was before.



    Someone pleeeeeeeeease tell me you've had this problem and fixed it, and what the fix was!!!
    • Member

    Brian A

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    Your link to realoem doesn't work btw. I plugged in the "&hg=35&fg=10" portion into realoem for a 1987 325e and got the following:
    http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=35_0123&hg=35&fg=10

    Springs usually don't wear out or act up. Its got to be in one of the pivot points or, more likely, the throttle cable itself.

    Working back from the engine, I assume you've checked the throttle valve already, You can articulate the throttle valve by hand without even disconnecting the throttle cable. See The Gospel According to Bentley -- Section 6, Chapter 4, Verse 6: "Accelerator Cable". The throttle should move open and close very smoothly, with lots of nice spring force pushing it back again to closed position.

    If that is smooth, then check the Accelerator Cable ("throttle cable"). Disconnect the throttle cable from the throttle body and try moving the inner cable back and forth in the outer cable to see if the cable binds. You might need a new throttle cable.

    It sounds like you've cleaned the accelerator pedal mechanism quite thoroughly already. Still, there might be a pivot point that is binding. You'll need to visually inspect and maybe take some of it apart. Its always great fun working in the footwell.

    Don't forget too that it might be a Motronics gremlin. In that case, take up drinking.
    • Member

    az3579

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    Why would it be a Motronics gremlin if the pedal is physically sticking and not acting up electronically?


    The cable is fine. I've tried to rev the engine from the engine bay and it is absolutely smooth from that end and returns to normal position when I let go. I seriously doubt it's the cable.
    • Member

    Brian A

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    Glad to hear its clearly isolated at the pedal.

    Re Motronics, I mentioned it only because it was unclear in your original post how much diagnotic or problem isolation work you'd already done.
    • Member

    az3579

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    Yeah, I forgot to include those things. Check the time stamp; I was clearly tired when posting. :)


    Everyone who has replied on Bimmerforums says #12 cannot be it, and they all say the bowden cable is to blame. I really don't feel like paying $30 for a cable when I know that the cable is smooth at the engine. That would completely rule it out, right?
    • Member

    Brian A

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    "Bowden Cable" is yet another term for "throttle cable" or "accelerator cable". It certainly is THE leading suspect in the crime.

    Can you disconnect the Bowden Cable at the pedal and see if the pedal mechanism itself is sticky? That will isolate a pedal problem from a cable problem.

    EDIT:
    Throttle cable is NOT ruled out by what you've described above. You've confirmed smooth operation of the throttle butterfly by manually "rev-ing" the engine, but this bypasses the Bowden cable. A Bowden cable is like a bicycle brake cable; it consists of thin flexible wire inner cable surrounded by a outer sheath. It connects the throttle to the gas pedal. The Bowden cable stays stationary when you manually rev the engine. It connects to part 2 (Operating Lever) this diagram:
    http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=13_0330&hg=13&fg=15
    • Member

    MGarrison

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    not to sidetrack the thread here, but THAT was freakin' hilarious, g1 Brian! :D
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    • Technical Service Advisor

    mooseheadm5

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    I'll post back in a bit, but you can lube the cable (14) and check your bushing at the pedal box (7) and the pivot at the pedal (top of 1 where it slides over 5.) Don't use WD40, it'll just make a mess. Remove, clean, and grease with silicone grease. Check cable for kinks or small diameter bends.
    • Member

    az3579

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    What kind of auto store would carry it? I'd try the closest one (Advance Auto) but they don't carry some of the simplest things. There's an Auto Zone nearby, perhaps them?
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    • Technical Service Advisor

    mooseheadm5

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    You can lube the cable with graphite lube or any number of various spray lubes. Silicone grease is also commonly found as dielectric grease or brake caliper grease. It does not split up like petroleum grease does. Any auto parts store should have it (I remeber how much your Advance sucked from the painting thing, but they should have the lubes you need.) BTW, if this stuff is binding it can cause the idle issues you are experiencing.
    • Member

    az3579

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    No, it is not the cause of my idle problems. I seriously doubt it's binding that much to rev 3500RPM...

    Besides, throttle response is normal when it's revving 3500, so if I lightly tap the throttle when it's "idling", then it doesn't go up much but if I give it more of a shove then it does. Typical, as if you were holding the throttle at 3500RPM; response wouldn't be much if you pressed just a little bit more.
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    • Technical Service Advisor

    mooseheadm5

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    It is a possibility, though. You could always try to close the throttle manually just to make sure.
    • Member

    az3579

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    Tonight, after 3 hours, I finally replaced the throttle cable. Damn that square black plastic piece on the interior-side of the firewall!



    This completely fixed my problem with the throttle. I now know why my previous throttle cable was so choppy; the actual wire itself started to cord, and it was catching on whatever it was catching on when that part of the cable was used, resulting in really choppy levels of throttle input.

    My shifts are absolutely perfect now because I can now ease on the gas instead of having it On or Off like before. Heel and Toe downshifts will take some getting used to though because the pedal feels a lot firmer and the pedal travel from no throttle to full throttle seems to be a bit shorter. I'll verify that I'm getting full throttle with a helper tomorrow.



    Thank you all for your help, and I especially thank MGarrison for his continuing patience throughout the ordeal (ask me how I know). :)
    • Member

    MGarrison

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    Until you check it out, you might want to avoid fully flooring it, in case in the car's history someone already adjusted the pedal stop down - you wouldn't want to prematurely stretch the new cable. Make sure the pedal stop is set so as to not allow the gas pedal too far down (and thus, stretching the cable).

    Glad you got it together - what a freakin' hassle! Glad I could be of some help, moral support if nothing else :p

    Lube your throttle body a bit - spray some WD40 on parts 9, 12, 3, 8 - generally the top moving parts of the throttle body -

    http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=13_0330&hg=13&fg=15

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