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RE: VDSTS Norge Stepper Motor Test

seb

seb

Tuned and Synch'ed
Joined
Apr 12, 2009
Messages
61
Location
Bellingham, WA
For the last couple of days, my '07 Norge has been near impossible to start when cold. As well, over the last few weeks, the idle is totally erratic after a run and most times, it just dies . Usually after one or two restarts, it will settle down but I never know what it is going to do.
I plugged in my VDSTS after taking the bike for s short run today. The TPS is spot on and everything thing else looked OK. There is a stepper motor test function on the VDSTS. While the engine is running, this test starts displaying a screen number at 32 and by the time the number gets to 28, the VDSTS test hangs there awhile and then reports that the stepper motor failed.
Does this test work? Would the bike run at all without a functioning stepper motor?
 
Can't answer all your questions, but I have a couple of my own.

Have you emptied you condensate dump discharge tube? If the oil back flows into the air cleaner box it will muck up the TBs and make it run crappy. It's clears up on its own after while once the tube is cleared.

IIRC, the stepper motor test is performed while the ign. is on and the motor is off. Not sure if VDSTS has two stepper motor tests.

When starting, do the problems go away if you hold the throttle slightly open?

Seems to me that the stepper motor does not affect motor in the closed loop mode but I'm read the contrary here on GT so the experts say yes. A failed stepper motor does affect the motor. It's definitely critical at start up, open loop.
 
The stepper's function is to control idle speed. The lower rpm range is when the engine is on closed loop, but closed loop metering doesn't take place until the lambda sensor heats up to deliver voltage readings to the ECU.

If the airbox has excessive oil accumulation, as Rafael referred to, that can impact the throttle butterflies and the air source for the stepper motor. If the ail line source for the stepper is clogged, the stepper cannot allow air into the intake tract to increase the idle speed.

So, perform the test with the engine off as suggested, also check the airbox drain tube (it should have a rubber plug in it at the bottom). If oil comes out, it wouldn't hurt to check and clean the inside of the airbox, the butterflies, and the line from the airbox to the stepper.
 
What happens if the line to the air box for the stepper motor is disconnected. Does it need vacuum from the air box to balance. If the line is disconnected does it cause a rough idle when cold??
 
canuck1969 said:
What happens if the line to the air box for the stepper motor is disconnected. Does it need vacuum from the air box to balance. If the line is disconnected does it cause a rough idle when cold??
Click to expand...

There is no vacuum in the airbox. The airbox is a clean air source for the stepper motor. If the line is disconnected, the stepper would get unfiltered air. If the line to the stepper is plugged, then it would not function as designed. Some have found that beneficial, others not.
 
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