Re: e28/m30 semi-warm start problem

[rusmaster <rusmaster@xxxxxxxxxxxxx>]

Rob,
    The low rpm when warm may be due in part to the DME caught between
being cold and warm.  This situation is a result of the sensors not
being cold enough to richen the fuel mixture but not hot enough to run
as if the car is completely warmed up.  I will say though that it should
still idle OK enough to not a problem.  If it's only 2-3 seconds, I
wouldn't worry about it untill it gets worse.  somtimes the coolant
temp. sensor can go bad.  But if thats the case, I would suspect other
things would be real bad.  It could be the cold start valve also.  I
would highly recommend a Bentley manual if you are attempting to try and
diagnosis the fuel injection.  These are resonably complex systems that
take great care and specialized tools to debugg properly.

Tha flat spot can be due to the transfer pump in the gas tank.  The E28
have 2 fuel pumps, one in the tank and one under the car.  The xfer pump
is located in the tank via and access panel.  I changed mine bad one out
2 months ago and the cars acceleration smoothed out considerably.
Again, the Bentley manual is and invaluable resouce if you plan on
debugging yourself.  The Electrical Trouble Shooting guide from BMW is a
great resource also.  Although, it helps to be an electrical eng. to
understand some of it.

Good Luck,
Russ

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