Re: Wierd Motronic Symptoms...Help!

[BOBINYELM@xxxxxxx]

A while back I had a problem which I thought went away with the 3.2l engine 
in my '84 733i (automatic), but evidently has returned in a mutated state.

The engine runs perfectly and idles well (idle/full throttle switch set up 
correctly), but if while cruising above 1500rpm, the throttle is released 
quickly, the engine is essentially dead (no spark or fuel injector signals) 
until the rpm drops below 1500 at which time the engine acts as nothing was 
ever wrong (until the throttle is again abruptly reduced). If one gently 
reduces the throttle while above 1500rpm, this does not happen.

My old problem was the mirror opposite: that is that the engine would 
accelerate fine UNTIL 1500 rpm was reached, at which time the engine lost 
spark and fuel injector signals until the rpm fell below 1500, at which time 
it would again merrily accelerate until the magic 1500 was reached. This 
problem was "solved" by reconnecting a wire that led to a small black 
cylindrical object (cigarette diameter) about 1" long withe a diode symbol on 
it located right by the fuse/relay box. The wires are green with brown stripe 
and some go to the short bright aluminum rectangular sealed (potted) device 
plugged into one of the external relay sockets attached to the fuse/relay 
box. I believe it has something to do with the fuel vapor purge system.

Now I notice that if I plug the wires into the object I get symptom one, but 
if I unplug the wire, I get symptom two. 

Also, with the thing plugged in, after shut down one of the relays outside 
the fuse/relay box stays energized unless the battery is disconnected, at 
which point it releases and stays deenergized even if the battery is 
reconnected. Obviously, this is not condusive to long battery life.

The last part of the puzzle is that after each engine start, neither evil 
symptom appears until after several throttle on/off cycles are performed, at 
which point it predictably happens every time.

I have swapped about every component (AFM, DME, shiny potted "relay") with my 
'84 633CSi (5spd) and the symptoms don't change or follow the components, but 
rather stay with the 733i.

Sorry to take up so much bandwidth, but I am again contemplating buying 
comprehensive insurance anticipating a suspicious fire that will consume the 
car, but I know that is a bad idea. Anyone had a similar problem?

Thanks,
Bob

'84 733i
'84 633CSi
'87 535is
'82 B9 3.5 e23 Alpina

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