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  1. #1
    Active Lancista jolly500's Avatar
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    Steady 'high' idle?

    Hi.

    I know idle speed has been discussed before but I think this maybe slightly different?

    Car is 1969 Rallye S, standard in all respects.

    The carbs have been balanced, timing is spot-on, in fact the motor runs beautifully, no flat spots, no stumbling and if left to idle, is rock steady at just over 1000rpm.
    But I can't get the idle below 1000rpm and that is with the idle adjustment screw basically screwed totally out of the carb.
    I have checked for air leaks but understand that an air leak will result in a fluctuating idle so don't believe it is that.

    Does anyone have any other ideas what I could check for?

    Thanks
    Steve

  2. #2
    Legendary Lancista lancialulu's Avatar
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    Re: Steady 'high' idle?

    When you have screwed out the throttle adjuster can you pull back the throttle spindle overriding the rather weak return spring?

    Have the carbs ever been serviced??

    Is the balance screw next to the throttle tick over scre in the middle adjusted correctly. Normal point is near or at the lowest running of all cylinders as a quick check. It is easy for the crew to keep one carb out of sync with the other and effectively the engine without load runs on 2 cylinders while the other is shut.

  3. #3
    Experienced Lancista tangmonster's Avatar
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    Re: Steady 'high' idle?

    my 2c

    Spray some carb cleaner directly at the two areas i encircled in red below image and make certain there isn't change in idle speed.



  4. #4
    Legendary Lancista bmarler's Avatar
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    Re: Steady 'high' idle?

    are you certain of the rpm reading you're getting? the factory tach can be off a bit. you should be using a digital or calibrated analog tach for adjusting the carbs.
    in addition, if you can't get the idle down under 900 (i think) the advance weights come into play so your timing reading may be off as well.
    properly adjusting these carbs takes a considerable amount of time so don't be in a rush when doing it.
    the suggestion to spray carb cleaner at the throttle shafts is valid, i'd spray it at the rubber mounts too. and if there's a vacuum brake booster you might plug that hose off to see if it changes anything.
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

  5. #5
    Legendary Lancista Marnix's Avatar
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    Re: Steady 'high' idle?

    Heu... I am afraid I think of around 10 different reasons for a high idle… I am sorry about it, but diagnosing a carb problem remotely is very hard to do

    You can test for an air leak at the spindle openings (unlike in the figure, it is most likely at the ends, not in the middle). Spraying with WD40 or similar on the carbs and rubber interconnection is a first test yes.

    But otherwise, take them out, take them apart, clean out completely and start looking for play or air leaks (the butterflies scraping out at the side is another typical one)

    As I have said before, cleaning and removing all play and leaks usually fixes the problems usually for me (often without me knowing what the problem was really)

    Carbs are very delicate stuff. It is almost like watches.

    May I give a quote from the Lancia maintenance for the C32 PHH as an example to show how narrow the tolerances are:

    "Attention: With Palmer measure the diameter of the butterflies along the line of the shaft, to make sure that they are 31.96 mm, otherwise replace the butterflies (originally on carburetors of this type, this measurement was 31.98 mm , subsequently reduced to 31.96 mm)."

    They are talking tolerances of about 1/100 of a mm... it is that narrow. Few people realise that you got to work that precisely to get carbs in good shape.
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
    Alfa Romeo 33 1.4IE 1993

  6. #6
    Active Lancista jolly500's Avatar
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    Re: Steady 'high' idle?

    Thanks you everyone for your suggestions.

    I had hoped to start working through them this past weekend but never got to it.
    Will try next for weekend and report back.

    Steve

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    Experienced Lancista AB095's Avatar
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    Re: Steady 'high' idle?

    I had a similar problem, took off carbs & found the butterflies had scraped the carb body to the point where there was a visible gap around the butterflies. Took it to a local expert, they machined some oversized butterflies & milled the body to fit. Cured the fast idle but was an expensive exercise! You can buy standard spindles & butterflies which may help. https://www.pieces-fulvia.com/carbur...300.htm?page=2

  8. #8
    Active Lancista Astonish's Avatar
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    Re: Steady 'high' idle?

    Quote Originally Posted by AB095 View Post
    I had a similar problem, took off carbs & found the butterflies had scraped the carb body to the point where there was a visible gap around the butterflies.

    I am really curious as to how this can happen, I have seen other posts here which mentioned gap around the butterfly discs and I ask myself how does wear occur beyond the circumferential point of contact? Please forgive me, I am not being argumentative but my experience with fixed choke carburetors is limited to Weber DCOE and IDF and of those the mileage was restricted to race only or under 10,000 Kms of road use.
    Michael Rigby '72 1.3S S.2

  9. #9
    Legendary Lancista 1,6 HF's Avatar
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    Re: Steady 'high' idle?

    Quote Originally Posted by Astonish View Post
    I am really curious as to how this can happen,...

    If the spindles and/or their bearing surfaces wear, the butterflies can shift, in which case they'll rub the barrels
    Ed Levin
    Fulvia 1,6 HF

  10. #10
    Legendary Lancista Marnix's Avatar
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    Re: Steady 'high' idle?

    Quote Originally Posted by Astonish View Post
    I am really curious as to how this can happen, I have seen other posts here which mentioned gap around the butterfly discs and I ask myself how does wear occur beyond the circumferential point of contact? Please forgive me, I am not being argumentative but my experience with fixed choke carburetors is limited to Weber DCOE and IDF and of those the mileage was restricted to race only or under 10,000 Kms of road use.
    There are a number of reasons why for the Fulvia carbs the butterflies can scarpe the body. But not sure the audience here really want another "lecture" from me...
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
    Alfa Romeo 33 1.4IE 1993

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