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<e28> Dead 528e Update

[btw, i'm not that dumb - really - the "motrinic" in the subject line
of my posting yesterday was a typo...]

many thanks to all of the kind suggestions i received.

well, resident motronic guru jim c. confirmed my suspicion that the
speed sensor was at fault, so when i called the shop and they
suspected the same, i decided to let them replace it.  they wanted
$100 labor + $50 diagnosis fee to replace it even though i was the one
who wasted 1.5 hours going to their shop to disprove their initial
misdiagnosis of a "bad computer."  at least they were reasonable
enough to cut the $50 diag fee after i badgered them about it.  i
haven't picked up the car yet, but i'm pretty confident that the
problem is solved...

back to speed sensor diagnosis.  bentley's "test" is pretty lame.  all
they expect is a 960 ohm static resistance (engine stopped), which my
sensor passed. what's more important is the _dynamic_ behavior of the
sensor.  i think some sort of blinking LED test would be infinitely
more useful.  wait a sec...i think my idle faq has that...

boy am i an idiot.  i wish i'd read my own faq before towing the car
to the shop.  in section (3) of "Checking then ICM Inputs," there is a
blinking LED test for the ICM's "RPM Sensor."  My guess is that this
is exactly the same input as the "Speed Sensor" input to the DME (can
anyone confirm this?).  So if you're in doubt about the speed sensor,
you might want to try the blinking LED test if bentley's resistance
test passes.

Jim C. also says that tapping on the sensor while the
car is running is a good test (i guess if you can get the car to run,
that is!)


here is a synopsis of some suggestions i received which may help
others w/ similar problems:

1) cold soldered joints in dme box:  sometimes cold soldered joints
cause intermittents.  soln: reflow the joints.  this was ruled out in
my car by swapping dme boxes w/ my other car.
2) bad dme or fuel relays.  flaky relays can cause flaky running.
this was ruled out in my car by 1) swapping relays w/ same part
numbers in my car 2) shunting pins 87 and 30 of the fuel relay to
bypass the relays entirely.
3) a dead transfer pump can cause low fuel pressure.

- -sam