[SierraDan]

stuffed up my mixture screw setting thinking it was my idle now i dont know where its meant to be and my car wont run properly, smoke is coming out the back now so is it running too rich?

does anyone have an idea of a sort of standard position for it? even a ruler measurement?

[steak_knife]

wind it in till in near die's, then slowly wind out till you hit the "sweet spot", some say 1/4 out once it start's to die, doesn't always work..

[Teracis]

Actually I think I read that the other day in the full service manual, it came back when stekkie said it, it's not exactly that, but if you use his advice and consult the manual you should be right!

[SierraDan]

I screwed it all sorts of crazy ways so I couldn't even start it. I screw it all the way in then out 3 turns then adjusted from there. I think she's right now

Cheers guys.

[Ben_Sierra]

My Sierra is also rich...

Can someone please confirm for me which is the mixture screw, as I'm not sure I've got the right one (it doesn't seem to help)...

[royce]

comes out of the base of the carb at 90 degrees on the side closest to the rocker cover, there are a few vacuum lines all plug into the carby near it

note from factory it has a cap over it so it cant be adjusted, so may not be obvious as a screw

[SierraDan]

I got it tuned eventually. Not worth mucking with unless you KNOW what you're doing

[Ben_Sierra]

royce wrote:

comes out of the base of the carb at 90 degrees on the side closest to the rocker cover, there are a few vacuum lines all plug into the carby near it

note from factory it has a cap over it so it cant be adjusted, so may not be obvious as a screw

The carby's been rebuilt once so the cap has most definitely gone I would say...

Its not the one hidden under the throttle mechanism that you have to open the throttle to get to? Or is that something else...?

[royce]

that is the cold idle speed for the choke

[Ben_Sierra]

Ah k cool, its dark now but I'll have a look in the morning...

[stockman]

Is it the one with the spring on it?

[stockman]

[royce]

bingo, one at the bottom, one higher up and to the right is normal idle speed

[Teracis]

royce wrote:

bingo, one at the bottom, one higher up and to the right is normal idle speed

I thought it was only an idle mixture screw?

Are you saying that I could possibly have a tuning issue as the only issue with my carby? I Turned that screw out a couple of times to get the thing to idle nicer when I was reinstalling the carb after the rebuild as the manual was telling me it was idle mixture and the main mixture was taken care of by the jets...

Someone please confirm!

[JrZook]

Teracis wrote:

royce wrote:

bingo, one at the bottom, one higher up and to the right is normal idle speed

I thought it was only an idle mixture screw?

Are you saying that I could possibly have a tuning issue as the only issue with my carby? I Turned that screw out a couple of times to get the thing to idle nicer when I was reinstalling the carb after the rebuild as the manual was telling me it was idle mixture and the main mixture was taken care of by the jets...

Someone please confirm!

Yes besides all the choke adjustments there is only an (1) idle mixture adjustment screw. Rest of the tuning is fixed by teh jet sizes

[royce]

Teracis wrote:

royce wrote:

bingo, one at the bottom, one higher up and to the right is normal idle speed

I thought it was only an idle mixture screw?

Are you saying that I could possibly have a tuning issue as the only issue with my carby? I Turned that screw out a couple of times to get the thing to idle nicer when I was reinstalling the carb after the rebuild as the manual was telling me it was idle mixture and the main mixture was taken care of by the jets...

Someone please confirm!

First, dont quote a sentence where I am reffering to 2 screws and say THAT one, which friggen one there are 2!

2nd, all they adjsut is idle mixture and idle speed, once you are into enough engine speed to move the car they are well and truly out of the game, closest running adjsutments you could get is if the mixture is lean you might get a bit of a stutter as it transitions from idle to primary but youd never pick it in a sierra.

[stockman]

Does anyone know the function of this plunger? I know it sqirts fuel, but is it for idle, take off or something else?

[royce]

its the accelerator pump, squirts fuel when you push the throttle as without it there would be a delay in the venturis sucking more fuel out so you get a big flat spot, this covers it

its also a god place to start looking when you get a hesitation when accelerating

[stockman]

Not what I'm looking for then.
Most of the time the car idles prefectly but every now and then the idles real low and rough and the stalls.
What do you think that would be?

[royce]

give the carb, especially around the linkages a real good clean to make sure its not normally being held high at idle and then dropping back too low sometimes

around the other side is a box with 2 hoses going to it, this is an air bypass at high temp to stop low idle from thin hot air, might be blocked but I doubt its a problem down there

[stockman]

Interesting. High Idle is different to choke?
What's the purpose of high idle and what is it set at.

[Teracis]

royce wrote:

Teracis wrote:

royce wrote:

bingo, one at the bottom, one higher up and to the right is normal idle speed

I thought it was only an idle mixture screw?

Are you saying that I could possibly have a tuning issue as the only issue with my carby? I Turned that screw out a couple of times to get the thing to idle nicer when I was reinstalling the carb after the rebuild as the manual was telling me it was idle mixture and the main mixture was taken care of by the jets...

Someone please confirm!

First, dont quote a sentence where I am reffering to 2 screws and say THAT one, which friggen one there are 2!

2nd, all they adjsut is idle mixture and idle speed, once you are into enough engine speed to move the car they are well and truly out of the game, closest running adjsutments you could get is if the mixture is lean you might get a bit of a stutter as it transitions from idle to primary but youd never pick it in a sierra.

I apologise, good to know I was right with what I originally thought then, pity it's still gonna cost m $400

[SSSIERA]

i got a webber on mine, it seams to spit/ spray black shit out that back, no smoke but. i have a feeling the webber might need rejetting? any idears

[nissvit]

[quote="Teracis]
I apologise, good to know I was right with what I originally thought then, pity it's still gonna cost m $400 [/quote]

What is going to cost you $400???

[JrZook]

SSSIERA wrote:

i got a webber on mine, it seams to spit/ spray black shit out that back, no smoke but. i have a feeling the webber might need rejetting? any idears

Condensation mixed with crap in the pipe. As long is it aint running like a dog all should be sweet!

[Teracis]

nissvit wrote:

[quote="Teracis]
I apologise, good to know I was right with what I originally thought then, pity it's still gonna cost m $400

What is going to cost you $400???[/quote]

Full carby overhaul, I've been told it will make it as good as new!