High revs

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fastandloud
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Tue Mar 12, 2019 12:19 pm

Hi I converted my 318 m10 to 2.5 m20 car starts and drives perfect with only one problem on first start up the revs shoot up over 2k and gradually come down after that it doesn't happen again until the next day on first start up again I've put on a new icv changed airflow meter and had injectors refurbished and it still does it there's no leaks or anything around intake manifold. Changed the blue temperature switch and still the same any ideas what it could be
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Brianmoooore
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Wed Mar 13, 2019 7:01 pm

If the engine revs higher than it should, then it is getting the necessary air from somewhere!
Any sign that the screw on the throttle body that sets the closed position of the throttle butterfly has been 'adjusted'?
Needs a special BMW tool to set up properly, but the method I use is to remove the ICV, block both ports, start the engine (you'll need to manually hold the throttle slightly open), then set the idle revs at around 400 - 500 RPM. I.e. a very lumpy idle, with the engine rocking around and threatening to stall.
If the throttle stop is changed, then the throttle position switch will need to be set up as well, so that it switches immediately after the butterfly leaves its stop.
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arrisbmw
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Thu Mar 14, 2019 1:47 pm

mines the opposite to that. revving too low on cold start ups . i,ve changed thr same items as you or tested them.
Car runs fine when warm . My problem must be in the wiring somewhere , but i,ve checj that and cant fina an issue , i even tried another e.c.u .
with no joy. I am in the process o converting the icv to manual operation with steep down voltage pot.
if its sucessful ,i ,ll post it. but my m40 has a diff set up to yours only 2 wires to it , i think yours has 3.
unless youve keep the original fron the m40 engine.
sorry your was the m10 . i believe that had a differnt controller for the icv . a idle control speed modue . where as the later m40 was incorporated in the e.c.u.
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Brianmoooore
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Thu Mar 14, 2019 2:05 pm

arrisbmw wrote:
Thu Mar 14, 2019 1:47 pm
but my m40 has a diff set up to yours only 2 wires to it , i think yours has 3.
This is correct. The M40 ICV is an electric motor acting against a spring (defaults to shut). The M20 ICV is effectively two motors turning in opposite directions, acting against each other (has no default position - stays where it is when power removed.}
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