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Re: 535i Fuel Injection questions?

>Despite this, it has the following problems. Rough idle, surging under
>acceleration (comes and goes), much better performance when the engine is
>cold. It also seems that the low RPM performance is sometimes rough.

Ha! I'm not going crazy!  My 535 has always been like this as well.  I too
have tried to explain this to various mechanics and I usually get standard
answers like "they all do that"  well, maybe they do but it bugs the hell
out of me.  My suspicion is that the motronics is overly leaning out the
mixture under certain conditions (engine temp., intake air temp., throttle
position, etc.).  When the engine is cold, the mixture would tend to be
richer, resulting in better performance.  One thing I haven't tried is
adding a resistor in series with the engine temp. sensor.  There was a
service bulletin on this at some point although I think this is more of a
cure for cold starting problems.  It might help with lean surge as well...

  I've heard from various sources over the years that the mid 80's 533/535s
were set very lean from the factory, don't know if this is true (any input
Jim C.?). Another clue is that all reports I've read from other e28 535
owners who installed Dinan (etc.) chips claim dramatic improvements in
engine smoothness, power delivery.  Do I want a chip? You bet!
Unfortunately, mine is soldered in place.

As for the rough idle, well I'd get used to it and tell your friends you've
got a "hot cam" ;-)  It can be improved somewhat (email me for details) but
will probably never be perfect.  In this case, I think its a definite "they
all do that".

If you find anything, I'd really like to hear about it!

>Thanks,
>Nat Crutcher
>
>1985  535i, 104K mi.