BMW 3.0CSi throttle butterfly position

Barry.b

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Hi guys
I am looking for advice please.
I only just got my engine up and running and I don’t know if a previous owner has made adjustments to her or not, but I do know she is running way too fast on zero throttle.
My engine is ticking over at approximately 1900 to 2000 rpm so I believe it is getting excessive air from somewhere.
I have checked all intake manifold gaskets and the all seem good.
I have noticed that the butterfly on the throttle body does not actually close completely .
If I shine a light behind the butterfly I can clearly see light all around between it and the throttle body housing.
Is that normal or should it be closed fully ?

If it should be closed I think I might need to loosen the shaft clamp bolt as backing off the throttle stop screw does not seem to allow the butterfly to close. ( please advise)

Then can I also ask should I adjust the air adjustment screw to get her to tickover normally ?

I have already rebuilt the auxiliary air valve with a new wax bulb so I believe it should be working properly, although I might temporarily bypass that system just to rule it out.

Then one last question, I set all of the timing to TDC when putting her all back together, so I think that means that my ignition timing might need adjusting/ setting
Is there a “how to “ for that somewhere ?
 

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Barry - the butterfly is open too much.
Disconnect the linkage and adjust.
Remember the idle adjustment screw!
It’s on the firewall side of the throttle body down low.

You can call if you want.
 
Hi Don
Yes I was thinking that might be the problem alright.
I will make some adjustments to it and see how it goes
Thanks again
 
Hi Don
I don’t have any throttle linkages connected yet.
So my butterfly needed adjustment in the throttle body itself .
I loosened the clamp bolt and moved the butterfly to the fully closed position .
Now when I start her she is ticking over at approximately 450rpm and is nearly cutting out.
At least now that the butterfly is closed that is my base line and I think I need to adjust something else now.
Should I concentrate only on the idle screw now?
 

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Hi Don
I have read that with the butterfly closed I should be able to rotate the throttle switch slowly until I get zero resistance across pins 45 and 17
I cannot achieve that with my multimeter attached, it seems to stay “open circuit “ .
Am I missing a trick by any chance or is my throttle switch faulty ?
She has 1972 stamped on it so it must be an early one.
 

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Adjust the big idle screw on side of throttle body next
 
Adjust the big idle screw on side of throttle body next
Hi Don
I have adjusted the big idle screw and she is now ticking over at 850rpm on the rev counter. So she is much better now !
My next question is with a timing light looking at the mark on the front pulley what should timing be set to ?
should it be 22* at 1700 rpm or something ? I have read somewhere that the csi might be different on this than the carburettor models.
 
for a CSi it's 22 degrees at 2500 rpm but unless you have markings on your pulley, the flywheel ball through the hole in the bellhousing is used for timing that way.
 
Okay
I did try 22* at 2000 rpm earlier and she stalled out
She might not have been up to operating temperature though
So I think it’s definitely worth another try
Thanks again guys !
 
Mark the flywheel with paint. Mark the TO and the ball with different colors
 
Last edited:
I have just managed to find the marks and paint each of the 2 a different colour.
It also turns out, when I said earlier that I had tried it at 22* that was not correct
I hade measured the diameter of the front damper and had worked out it’s circumference then I divided it by 360 and multiplied that by 22 to give me an idea of where 22* is.
I printed that out as a scale of 1:1 so it was / is accurate.
Except that I put it on backwards so instead of advancing the timing 22* , I was actually retarding the timing by 22*
( or viceversa)
That might explain why it stalled :)
Anyway I should be able to give it another go and this time I will turn my sticker the correct way around and hopefully know what I am looking at.
Thanks again !
 

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