<e28> '87 535iS -- Intermittent Drivability Problem

["Tim Ketterson & Dulce Roman" <tukdmr@xxxxxxxxxxxxx>]

Fellow Digesters:

Though I've been a lurker on the digest for years, this is my first 
post to the group.  I bought my first BMW in mid-January and really 
have been enjoying my purchase...sort of a childhood dream-come-
true, if you know what I mean ;-)   "Karl Heinz", a name bestowed 
by the previous owner, is a very well-preserved 1987 535iS (mfg 
date 9/86) with 5-speed Getrag, Alpine White with Pearl Biege 
leather sport seats,  with 146K.  With the exception of the M5 
wheels (w/rolled rear fender wells), a short-shifter, and a Supertrapp 
exhaust the car is stock...which I prefer.  My wife and friends don't 
like the Supertrapp...I think exhaust note sounds GREAT in 
tunnels and parking garages ;-)

I have a fairly comprehensive service history on the car and after 
some research (e.g., Carfax report, etc.) I have learned I am the 6th 
owner!  That seems like I lot to me...should I be worried?  A couple 
of the early owners (both women) kept the car for less than a year. 
Perhaps they didn't like the "sportiness." The car was originally 
bought at South Motors in Miami, FL and has spent all of its life in 
Florida and the Atlanta, GA area.  Several enthusiasts have owned 
the car, including the close friend from whom I bought it.  

Sorry for the long intro...now to the heart of the matter.  I need help 
diagnosing an intermittent drivability problem that I can't seem to 
pin-down.  The problem has occurred 4-5X now and seems to be 
getting more frequent lately.  I first experienced it at the very end of 
my first 500 mile highway jaunt...on a rainy day (55 degrees F).  I 
had been cruising very smoothly in 5th gear around 80-85 mph 
when upon accelerating to pass a slower-moving car the "bogged-
down" whereupon I downshifted to 4th...continued to "bog" and 
then I decided to drop it into neutral and coast off the next ramp.  
During this maneuver, the engine dropped to idle and would not 
respond "positively" to the throttle. My attempts rev the engine met 
with an instantaneous reduction in RPM but...the engine never 
stalled-out.  At the top of the off-ramp I let the car idle for about 10 
minutes.  Since I was in "the sticks" and too afraid to shut it down. 
 I popped the hood could not locate any obvious problems.  After 
about 5 minutes I was able to rev the engine gradually to a "rough-
as-a-cob" 2-3K.  Soon thereafter I did a short test drive down an 
access road with NO further problems.  The proble did not reappear 
for 1 week or so.

About a week or so after the first episode the problem recurred.  It 
has happened an additional 4-5x during my daily city commute.  
For example, it happened 1-2x starting off at traffic signals, 1x at 
start-up (6pm today), 1x when going down a hill, and once when 
turning a sharp curve.  It always seems to recover quickly (4-5 
seconds) but I can't tell what is going on.  

On one other occassion, the car was parked on a very slight 
upgrade and it would NOT stay cranked.  It was really running rich 
too...my wife was gagging from the fumes.  This was also on a 
rainy day.  After a few minutes...it fired up and off we went...no 
further problems.

During all of these episodes...NO smoke, of any color, has ever 
appeared from the exhaust.  However, the car does smell like it is 
running a bit rich...but NOT always.  I am getting about 22mpg on 
the highway and 15-16 in town.  Is this in the normal range for the 
e28?

My rule-out diagnoses have included:   1) plugged catalytic 
converter or some other exhaust problem; 2) a fuel-delivery 
problem; 3) poorly seated relay(s) in the fuse box (note: car has 
'new' fuse box); 4) dirty throttle body?; 4) old spark plugs, wires, 
rotor & cap?; 5) water in the gas tank; 6) bad O-2 sensor.  Or a 
combination thereof? 

Well, I'm out of ideas and want to see what I can do to resolve the 
problem before taking it to the stealer.  I would greatly appreciate 
your ideas and suggestions.   Sorry for the LONG post...will keep 
future ones much shorter.   Many thanks in advance!

*********************
Tim Ketterson, Jr.
'87 535iS  146K
*********************

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