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Obscure Question B21F Idle Speed Control 200

posted by  yellowbrickroadster on  Sat May 28 10:02 CST 2022
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last visit: Wed Oct 22 06:18 CST 2014
[RELATED]

I have a 1980 242 with B21F and K-Jet. The idle speed adjustment screw is the black plastic thumb wheel type thingy under the intake manifold, attached to the front side of the throttle body. Does this black plastic adjustment screw unscrew completely in order to be removed ? I picked up a spare throttle body at the pick-n-pull and wanted to remove the black plastic screw to check for cracks, clean everything up etc. Has anyone here ever taken apart this idle speed mechanism on this version of the throttle body and then reassembled with new gaskets, o-rings or whatever ?








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    Obscure Question B21F Idle Speed Control 200

    posted by  machine man on  Sat May 28 21:30 CST 2022
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    last visit: Wed Oct 22 15:40 CST 2014
    [RELATED]

    Hi,

    The answer to your air mixture screw question is YES.

    It is made of a separate type material from the fitting its in. Nothing holds it per say as in not crimped into place like many parts of other car in the future of this machine. You can work on it.
    I have had mine out on my 1978 B21F. Done it maybe once in the car’s lifetime.
    About all you can do is clear any air entry ports and wipe off of carbon or oil deposits.
    The screw has a blunt but conical end. Simplistic as a carburetor’s fuel leakage screws.

    I gather you are wanting to be through this since it’s an aged car and could have an issues in there somewhere.
    A Cleaner throttle body is closer to an original breathing hole that it came with new. (:)
    Don’t forget to think about an intake gasket if its original too. Easy to lay back and change.

    Have you had a K jet system before or had this car for sometime?
    Are you just doing maintenance or having an issue with idle speeds when cold versus at operating temperatures?
    My 1978 GT has many mechanically set items and that black knob is only used on the K jets.
    I’m asking to find out if you are familiar with setting that throttle body and the auxiliary air valve per a service manuals instructions?
    These systems were preludes of lots of experimentation but done to overcome a carburetor’s morning emission issues.
    These times were before “buzz words” took over or “hybrids” were introduced by every white coat mechanic available to every company.

    No questions or statements are obscure here. (:-)

    Phil







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      Obscure Question B21F Idle Speed Control 200

      posted by  yellowbrickroadster on  Sun May 29 04:42 CST 2022
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      last visit: Wed Oct 22 06:18 CST 2014
      [RELATED]

      Thanks, Phil,

      Yes, I am quite familiar with K-Jet and this car, having had it since new ! I picked up another throttle body from a junk car, and wanted to go through that one so I would have a nice, clean, "perfect" one to swap into my car at some point.

      What is confusing me is that the black plastic screw backs out a few turns, then binds up and seems to hit a stopping point where it just spins and does not seem to move outwards any more. I didn;t want to force or break anything, so seeking advice from others who have gone down this path.








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        Obscure Question B21F Idle Speed Control 200

        posted by  machine man on  Sun May 29 12:35 CST 2022
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        last visit: Wed Oct 22 15:40 CST 2014
        [RELATED]

        Hi,

        Like I said it has been many years since I had one of those out.
        If I pass by the car today I will try to see if it still does.
        I’m pretty sure that it does come out or I wouldn’t know that it had the shape on the end.
        That whole assembly might be held on by two screws.
        The later LH system has the same screw even though it’s good for nothing because of the IAC on those cars. If it wasn’t that one, it was one of those on my other cars.

        As I remember there maybe an O ring on its body. It may have gotten hard and so it is no longer pliable.
        It does fit in there with some drag, so maybe it doesn’t want to play ball with you. Carbonized oil vapor? (:)

        I have own my ‘78 GT since 8,000 miles as it was the dealers service managers car. I paid $8,000 for it.
        It has somewhere above 350k on it. The odometer has quit several times despite my efforts.
        The speed needle works but the numbered shafts have worn their bores in the pot metal too much.
        It binds up or something slips.
        Many many years ago the gear drive housing, on the rear of the transmission, cracked and fell loose disconnecting cable.
        A cable tie has been holding it in place for the last twenty+ years. (:- hey it works. (:)

        On older American cars it was called a roll of hay farmers bailing wire.
        Talking about Heritage from Europe.
        In Sweden they call the Volvos “tractors.”
        That’s probably where the Amazon and the One series got their designs from. Our tractors had in-line engines too.

        All that has changed just a little bit didn’t it?

        Phil








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          Obscure Question B21F Idle Speed Control 200

          posted by  planetman on  Sun May 29 23:26 CST 2022
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          last visit: Fri Oct 24 09:29 CST 2014
          [RELATED]

          The idle screw can be removed.

          Try using some lubricant.

          FYI, new adjusting screws are still available as are the o-rings.
          --
          Eric
          Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
          Torrance, CA 90502
          hiperformanceautoservice.com or oldvolvosonly.com








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            Obscure Question B21F Idle Speed Control 200

            posted by  yellowbrickroadster on  Mon May 30 06:14 CST 2022
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            last visit: Wed Oct 22 06:18 CST 2014
            [RELATED]

            Thanks again for the helpful info. From the parts diagram the idle screw indeed looks like it can be removed. The one I am working on reaches a point when backing it out where it just spins, and does not wind out anymore. My thought is that the thread on the plastic screw may be stripped and not gaining any traction. I've ordered a new screw and o-ring, and now feel safer about working the old one out.







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