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Thread: Another high idle thread - how-to on butterfly plate springs?

  1. #11
    My friends think I'm nuts jawn101's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Post a photo of the deceleration springs. You pull the W pipe and move the throttle and you can see them. If they are not evenly spaced, they are bad.
    Okie doke. Here are the pics. TBH, these look pretty ok to me.


    IMG_0348.jpg

    IMG_0349.jpg

    IMG_0350.jpg
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
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  2. #12
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by jawn101 View Post
    Okie doke. Here are the pics. TBH, these look pretty ok to me.


    IMG_0348.jpg

    IMG_0349.jpg

    IMG_0350.jpg
    Yes, those look good.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #13
    My friends think I'm nuts jawn101's Avatar
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    Hmm. Then what else could it be? I had a friend suggest that the idle motor might be sticking, I havenít investigated that yet.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
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  4. #14
    Delorean Guru
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    One possibility is that the throttle arm is not being returned ALL the way to the idle stop position. That can happen if you develop a lot of play (looseness) in the rod ends of the quadrant link or the throttle cable or throttle spool is sticking and not moving smoothly and easily. Verify that the idle switch is getting "set" when you release the gas pedal. If anyone messed with the idle stop screw and/or the idle switch adjustment the throttle plates may not be fully closed and if the air screws are not closed air can be bypassing through them. Just a few more things to check.
    David Teitelbaum

  5. #15
    My friends think I'm nuts jawn101's Avatar
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    Quote Originally Posted by David T View Post
    One possibility is that the throttle arm is not being returned ALL the way to the idle stop position. That can happen if you develop a lot of play (looseness) in the rod ends of the quadrant link or the throttle cable or throttle spool is sticking and not moving smoothly and easily. Verify that the idle switch is getting "set" when you release the gas pedal. If anyone messed with the idle stop screw and/or the idle switch adjustment the throttle plates may not be fully closed and if the air screws are not closed air can be bypassing through them. Just a few more things to check.
    Thanks, but as I mentioned the quadrant arm and throttle spool seem mechanically correct, and the idle switch is engaged. Both screws have their factory paint marks intact and nobody's touched them. Brass screws are all closed tight. Pushing the throttle arm "more closed" when the idle raises while warm doesn't change anything.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
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  6. #16
    Delorean Guru
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    Well, you are getting "false air" leaking in somewhere then. Either you find it visually or you do a smoke test to find the leak. A missing gasket, a leaky hose, something. On one car I found a leak, it was on the right side intake runner, front surface, the seal plug was squished because someone used too long a bolt on the ground connection and it bent the seal plug. Vacuum leaks can be difficult to find. On another car the "O" ring was missing on the cold start valve. Often the injector seals leak. Also common for the tube to the idle motor "O" ring on the bottom of the mixture unit. Point is you have to look for the unusual.
    David Teitelbaum

  7. #17
    My friends think I'm nuts jawn101's Avatar
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    Yeah, a smoke test isn't a bad idea. I just replaced the injector seals a few weeks ago, actually - new clips, too. I know the CSV has the O-ring on it, and the idle air pipe has a new o-ring as well as RTV holding the brass cup down just to be sure.

    I do know that the oil filler cap doesn't seal, and I've tried replacing the o-ring but it never seems to be the right OD. It sort of floats on top of the neck. Also my dipstick doesn't seat fully; it doesn't seem that the rubber portion can be moved on the metal, and I don't want to nip the end of the stick since that would impact how it measures (not that I use it for that)

    The odd thing remains that this is only happening warm. Wouldn't a vacuum leak be present no matter what?
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  8. #18
    My friends think I'm nuts jawn101's Avatar
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    Just a little more troubleshooting: I removed the idle motor and sprayed it out with some penetrating oil, through the intake side only. It really wasn't very gross inside. Reattached it and made sure the seals to the idle air/CSV pipes were good. Didn't really make a difference.

    Now, on day 3 of fiddling with things, it does seem like pressing the throttle arm hard closed against the body changes the RPM. The microswitch is engaged, but mechanically it seems that something is still ever so slightly open internally. I tried adjusting the length of the quadrant arm slightly, you can do it in half turns if you flip it end over end - but that seemed to make it worse.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  9. #19
    Senior Member Bitsyncmaster's Avatar
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    Two things on my car:

    The throttle cable had worn through the outer rubber where it was clamped on the passenger side valve cover.

    Greasing the large throttle spring on the spool fixed my sticking throttle return.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    My friends think I'm nuts jawn101's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Two things on my car:

    The throttle cable had worn through the outer rubber where it was clamped on the passenger side valve cover.

    Greasing the large throttle spring on the spool fixed my sticking throttle return.
    Ugh, that long ass cable is the bane of my existence. Nobody ever intended that style of cable to be used like this. I did have an issue with the throttle sticking open that turned out to be me pinching the cable between the valve cover and airbox, which I resolved.

    There are two main springs back there, the one on the armature itself (vertically oriented, attached to throttle body) and the one inside the spool. I *normally* run without the one in the spool at all, since it makes throttle response way snappier, but I've reinstalled it to eliminate that as a source of problem here. I'm sure they could both do with some grease, but which did you mean? Sounds like the removable one?
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

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