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Old 03-31-2013, 02:57 PM   #26
johnjen
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Joined: Nov 2001
Location: Seattle
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Quote:
Originally Posted by billdonna View Post
Ok, this is where I disagree/get confused. Please correct me here if I'm wrong...

The "steppers" are actually the idle stops, a mechanical stop, ie.they set up the idle RPM by keeping the butterfly valves in the TB's open a crack to idle. They move up and down to make fast idle RPM as req'd by a cold engine temp. Yes?

If so then when balancing the TB's at 3500RPM, the idle stops are not touching the butterfly valves any more and do not need to be "parked". I balance my 2010 GS without using my GS911 to park the steppers and have a beautiful , smooth balance.

No chance of fouling up here if you do not park 'em!
Uh, no, the steppers are an electronic 'stepped' motor that opens (and closes) the idle air bypass circuit. In effect it replaces the Big Brass Air Screw found on the 1100 and 1150 throttle bodies. They electronically (from the fuel injection computer) control the idle for each cylinder instead of it being a fixed amount like the older 1100 and 1150 systems.

Many have reported that 'parking' the steppers is not necessary in order to balance the throttle cables. And while that may be so (I don't have a 1200 to play with this to verify it one way or another) BMW did go to the trouble of providing this function for that reason.

JJ
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