Weber 32/34 - Bogging at low throttle position when cold

Discussion in 'Carburettor' started by Megaross, Oct 22, 2019.

  1. Megaross Forum Member

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    The weber saga continues - rebuilt this and it's solved a lot of the issues I'd previously had with the weber on my mk2 1.8 GL (Auto). Dieseling, lack of power etc.

    When it's warmed up the car runs great, pulls strong and has no issues.

    However coming off the idle when the car is cold (a minute or two running) the thing bogs like a fiend and will stall if you aren't careful. Also seems massively down on power when the engine is cold.

    One thing I have noticed the idle mixture has to be set very rich, it's over 2.5 turns out at idle or it runs like horse shit. I've verified this a few times using engine noise/ feel and vaccum gauge the conclusion always comes out the same for mixture being set @1000rpm

    Accelerator pump is definitely working, you can see it squirting.

    Not really sure where to take it next, any ideas?
     
  2. pigbladder Forum Addict

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    if its cold is needing the choke out a bit still? mine still wanted a bit of choke for say 3 -4 miles if you stopped at a junction
     
  3. Megaross Forum Member

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    I tend to keep the choke out until it doesn't need it maintain idle speed (1500 in park tends to be around 1000rpm in gear - autobox)

    Doesn't make any difference though, choke in or out it still bogs until up to operating temp.
     
  4. Megaross Forum Member

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    Ok, I've had a look and the throttle channel preheater jobby from the pierburg 2e2 is missing, as is the exhaust manifold heat deflector thing and the pipe to the warm air feed.

    Could carb icing be the cause of the issues? The inlet manifold preheater appears to be working (gets warm with the key turn) but the other two bits of "get the thing warm" are totally absent. Not sure if anyone else has had similar issues with this?
     
  5. pigbladder Forum Addict

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    doesnt sound like carb icing but yeah wouldnt be a bad idea to replace it

    when i had it mine it kinda needed to warm up , it didnt drive the same hot and cold , could you be expecting too much from it?
     
  6. Megaross Forum Member

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    I mean I don't expect flawless fuelling from cold but bogging and stalling isn't normal.

    My old Jetta with a Weber didn't used to do that. And that ran like hell when it actually warmed up
     
  7. pigbladder Forum Addict

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    dunno then mess around some more , try a slightly bigger jet maybe , fastroad on ebay advised me on some tuning issues and got it right

    one thing i had wrong on mine was theres a screw to alter the idle when on choke ...i was having to pull the choke to maintain a cold idle but it was choking , so i added some revs so it would run faster with less choke if you get me
     
  8. Megaross Forum Member

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    I'll give them a shout.

    It could be the idle jet needs to be slightly larger given how rich I've had to set the idle mixture to obtain decent engine vaccum and running.

    I've set up plenty of bike carbs and done a a weber 32/34 fine before (including the rebuild) but this ones perplexing me.
     
  9. Simon Peter Dodgson Forum Member

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    Mine used to ice solid on cold day motorway driving. Defrosted before I could find the issue. Pita
     
  10. rubjonny

    rubjonny Administrator Admin

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    webers seem to be a little more forgiving of carb icing, plus your symptoms happen from cold and go away when hot makes me think its not that. if you're getting carb icing it doesnt care how hot the engine is, and the ice takes a little while to build up. once sat for a couple minutes after engine dies the ice melts and it'll run flawlessly again

    when warm air system wasn't working on my 2e2 carb the car would run perfect from cold and drive no problem for 10 minutes but cut out at the same set of lights every day. it would also sloooooooowwwwwly loose power on the motorway till eventually I could no longer maintain speed, then cut out on hard shoulder

    When I had our SPI polo running without the airbox you could watch the ice build up on the throttle flap!
     
  11. Megaross Forum Member

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    My thinking is its all too cold to properly atomise the fuel to the extent where it's leaning out like crazy.

    Might try a fatter idle jet then, play with the choke setup a little, swear at it, throw some mole grips across the workshop etc.
     

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