Motronic Questions

["Brian Franchuk" <Brian.Franchuk@xxxxxxxxxxxxxx>]

I have an 87 325 with the Motronic DME which uses the 15 pin 
diagonstic connector.  I've got the following questions:

1) Last summer with the A/C on, the engine would die if I let off
   of the gas and the RPM dropped from ~2000 to idle.  The engine
   would undershoot the nominal idle (700RPM ?).  Sometimes it
   would catch itself, sometimes it would die.  In addition, the
   idle speed would change while waiting at a stoplight, ie.
   first it would idle at 1000RPM for 10 seconds, then at 500 for
   5 seconds.  Could this be related to the airflow sensor going
   bad (the car has 126K miles)?

2) Sometimes when I start the car, it gets into a mode where it has
   no power at all.  It seems like the ignition is retarded.  To
   correct the problem, I just need to switch off the engine and
   restart (I didn't know I had microsoft inside).  This problem
   doesn't happen very often, once every other month, but it's 
   conserning.   

3) How does the DME know when to fire the ignition?  I know about the
   engine speed sensor and reference sensor, but this would only tell
   the DME that a particular cylinder is at either the top of the
   compression stroke or the exhaust stroke.  Doesn't the DME need 
   some signal from the camshaft to distinguish the two?  Any input
   on this would be helpful from any DME gurus out there.


Thanks for the help.

Brian Franchuk
87 325
88 535i

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