The E28 miss = the ECU!

[Howard K Mitchell <kmitch@xxxxxxxxxx>]

To all those who offered a diagnosis on my missing problem, I'd like to
offer a sincere collective THANK YOU!  The response was tremendous! 
Again, these digests simply amaze me in their usefulness as a
resource!   

Now on to the winner...  While many of the suggestions were surely very
likely culprits, it turns out that it was indeed the ECU.  I installed
a remanufactured one just before a round trip to B'ham the other day,
and the car hasn't missed once now in over 1300 miles. Congratulations
to Dana Earl, Don Eilenberger, both of whom were on the right track. 
First prize has to go to Rick Viehdorfer, though, who hit it right on
the head:

(snip) "This isnt brain surgery - it shouldn't BE that hard to trace
down the source of these niggling problems.

That being said, I will tell you that in my E28, I had similar problems,
and have been tracking problems like this for over a year, looking for
the holy grail.

There isnt one. It's the ECU (ECM). Its the Motronic 'box'. They go
funky. My car is on its third one since delivery. These problems range
from complete failure (Jim C will disgree and say they are all great,
but I've experienced it once. Deader than a doornail..) to weird
intermittent problems with mixture.. full-rich, stumbling hesitation,
etc.

The only thing that solves them is an ECU replacement." (snip)

Incidentally, I was reminded in a big way just how much of a difference
the JC/Turner chip makes.  When I got to B'ham I switched the chip from
my old ECU into the new one, and the difference was fenomenal!  The
effect was even more dramatic this time.  When I got the car originally
in '91 I had a chip installed; then this past summer I switched to the
Turner chip, and yes, I noticed a difference, but I didn't get the full
effect all at once like I did this time putting it in a stock ECU.  If
you're driving a E28 535i and still haven't gotten it chipped, it's the
best bang for the buck around for this engine!

Also, a couple of people wanted to know where to get remanufactured
ECU's.  I've used Programma for the SI board, and I understand they do
ECU's also; they advertise in the Roundel.  This particular unit came
from a company called Python.  I'm not sure if they are in the Roundel
or not.  I think both companies will diagnose and repair one for about
$200.

Hope all this will help someone else out there when theirs goes!
(BTW, I have no affiliation with any of the suppliers mentioned)

Ken Mitchell
Durham, NC

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