RE: Re: e28 M5 acceleration issues...

["Rodney Moore" <m6bigdog@xxxxxxxx>]

Robw,
The throttle switch only has two positions idle and wide open throttle.  The
part throttle positions do not use the throttle switch.  The common issue is
both idle and WOT do not use the Air Fuel Meter.
For a wild ass guess I'd suspect the AFM.  If the resistive element is
making intermittent contact it will cause the engine to drop-out/stumble and
then pick up again when the engine stumble causes the AFM to change
position.  After that I would take out an ohm-meter and start checking the
barometric and temperature (air & coolant) sensors.  There also is a
possibility your distributor cap/rotor and/or spark plug wires could be
failing during part throttle.
Regards,
Rod...



  Date: Sun, 27 Aug 2000 23:26:20 EDT
From: GRobWorkII@domain.elided
Subject: Re: e28 M5 acceleration issues...
James,
   I would suspect the throttle position switch.  The fact that you aren't
getting the hesitation at full throttle suggests that the switch is bad - it
reads three things:  idle, between 1 and 99% (middle ground), and WOT (wide
open throttle).  My guess is that the "middle ground" contact is shaky
Hope this helps,
RobW

In a message dated 8/27/00 10:10:10 PM Eastern Daylight Time,
owner-bmw-digest@domain.elided writes:

> Date: Sun, 27 Aug 2000 18:53:21 -0700
>  From: "James Nelson" <xi@domain.elided>
>  Subject:

>
>  Hi! My 1988 M5 exhibits fairly odd acceleration behavior---it can best be
>  described as a hesitation, and occurs mostly (always?) between 1% and 99%
>  throttle. It's almost as if the car can't make up its mind if it wants to
go
> or
>  not. Once I put the pedal down completely, however, there isn't much
> hesitation,
>  if any.
>
>  I bought the car in April, and previous to that it was in storage. It
> underwent
>  a thorough check-up (including hoses/belts/cat/etc. replacement) at the
> local
>  BMW specialist, it passes smog, and otherwise drives fine. Swapping
between
> the
>  JimC and BMW chips does not seem to make any difference in this arena.
I've
>  heard that vane-type airflow meters can cause a similar behavior, is this
> true?
>  Or is there a way I can determine if my AFM is actually on its way out?
Is
> this
>  a common problem on e28 M5's?
>
>  One other data point---it does not seem to accelerate as fast as I would
> have
>  thought. Our '89 750 keeps-up quite nicely with it, with such close HP
> numbers
>  (299 & 294) it would seem the e28 would win by a significant margin
(given
> the
>  weight/transmission). The e32 can't quite corner the same, though. :-)
>
>  TIA,
>
>  James Nelson...
>  1989 750iL
>  1988 M5
>  1975 2002



- ---
Rodney Moore
BMW CCA #86830
Golden Gate Chapter
m6bigdog@domain.elided

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