Re: <E28> Rough running

[Andrej Gaspari <aeg@xxxxxxxxxxxx>]

> I have an '82 528e that I have been wrestling with for several weeks now and
> am in need of ideas.  I presently have the car at a very reputable BMW repair
> only shop in Augusta, GA and they are also stumped.
> The symptoms: Starts fine, idles fine, runs great up to 2000 rpm, then cuts
> out and has basically no power.  Gas mileage is awful.
> What we have examined so far: Fuel pressure and flow rate - OK. Coil, plugs,
> wires, condensor, rotor - Checked all OK.  Air mass flow meter - put in good
> one to test - No improvement.  Motronic brain - put in a good one to test - no
> improvement.  Fuel injectors - put in good ones to try - no improvement.
> Vacuum leaks - None.  Catalytic convertor - checked but not stopped up.  O2
> sensor - Checked OK.  Speed sensor and TDC sensor - checked OK, but could be
> going bad at higher rpm; will replace next and then try.  Throttle switch -
> checked OK.

It sounds to me like you've got a typical fuel delivery problem, despite
having tested all the stuff you mentioned above. I would check the fuel
filter first - that's the most common cause of this exact problem. After
that, look at the main fuel pump, which may be on its way out. Also, the
tranfer pump might be contributing (check the FAQs on this one).
Finally, check for leaking lines - a partially cracked line may be
leaking sufficiently under running conditions to reduce fuel delivery
below the minimum necessary. HTH.
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