Intermittent miss '92 535i 5sp

[Jon Brush <jonbrush@xxxxxxxxxx>]

Hello Bimmerphiles: Apologies in advance to anyone who has already followed
this discussion on the E34 5er board. I'd like to see if this group has any
ideas.

Several of us E34 535iers have had the following problem without solution:
while tooling along at part throttle (almost trailing throttle), and low
rpms, hit a sharp bump. 1-2 sec later, the engine will miss, then continue
running as before. This is a *very* intermittent problem, at least in my
car; I can drive for a week without noticing anything, even over the same
bumps on my daily commute, then may experience the problem one or two times
the same day, then again a long interval. Several attempts to find the
fault have revealed no codes in the computer, and one mechanic with an
expensive diagnostic machine hooked up to the car's electronic brain found
no faults while driving around for a while. This is a well-maintained car
with no other electrical problems, no problems with the speedo or computer,
lights do not flicker, etc. One other owner said that his car with the same
symptoms showed a fault code in the road speed sensor, but had not had this
looked at. My car has not shown this code.

I should say that I did hit a sharp bump once while driving at highway
speeds,at around 2500 rpm, with the cruise control engaged. The cruise cut
out. I don't know if this is the same problem. I have speculated that
possibly the miss also occurs at higher rpms and larger throttle openings,
but is only noticable at lower rpms and tiny throttle openings because the
drive train is "barely" under power and the very brief miss causes drive
train lash as the power cuts out for an instant and then comes in again.
This is speculation on my part.

My solution so far is to avoid small throttle openings and low rpms when
hitting a rough patch of pavement :^) but this is not always possible...

Any ideas would be appreciated. Replies on the digest or to me directly are OK

TIA
Jon Brush@domain.elided
'92 535i 5sp 67.5K
'90 Cairn Terrier, tail happy most of the time

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