<E28> Stumbling engine/running rich

[khensley@xxxxxxxxxxxxxxxx]

Hello all!  A few weeks ago I posted that my idle on my 1985 535i was 
erratic.  Right after posting the problem, it quit.

Now, things are back with a vengeance!
The car won't hold an idle unless my foot is on the accelerator.
The exhaust appears black at time (incomplete combustion or running 
rich).
Once the car is running, no problem - until I let off the 
accelerator.  Even when changing gears, the brief period of time off 
the accelerator, the engine is stumbling.

Now, is this the idle control valve, the throttle switch, both, or 
something entirely different?

Private replies are fine.

...Kim Hensley
BMW CCA #16216

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