E34 (525i) Rumbling engine

["Gary Peterson" <gpeter@xxxxxxxxxxxxxxx>]

I hope someone/anyone can offer advice on what is causing my car to rumble
like a truck while idling (worse when in "drive").  It is also stumbling badly
(like a rev limiter being triggered) when the engine reaches approx. 3700 rpm
while accelerating hard.  It does not stumble if I accelerate gently through
3700.

History:  The problem seemed to start after getting the car back from valve
adjustment and tranny fluid change about 3000 miles ago.  The first thing
tried was replacing the spark plugs with factory Bosch units (did have
Champions in it).  The stumbling seemed to diminish for a while but it started
to return.  The rumbling was not affected by the plug change.  The next thing
tried was replacing the plug wires with no luck.  After the wires a new
catalytic converter was installed and, again, no improvement.  The last thing
done was replacing the rear exhaust resonator.  This made the exhaust a bit
quieter but the rumble remains.  I have checked the valve lash adjustment and
it seems OK.  Compression was also checked and is OK.

Many $$$'s have been spent with no appreciable improvement and I am at the end
of my rope.  Me and my mechanic are running out of options.  I am offering a
free fruitcake (or perhaps multiple fruitcakes depending on how many I receive
as gifts) to anyone that can help.

Thank You!
Gary Peterson
gpeter@domain.elided

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