Re: Tech question...engine miss

[alex.fadeev@xxxxxxxxxxx]

Michael <mike5635@domain.elided> wrote:
>
> I have a 1990 535i with about 135,000 miles on it.
> Several weeks ago, the engine had been missing,

Bad, bad engine. Did it come back?
(sorry, I could not resist ;-)

> and I replaced the plugs wtih Bosch platinum.  Seemed
> to work fine.  My brother-in-law was driving on the
> expressway through Chicago, and all of a sudden the
> engine started missing BIG TIME!  He made it home, but
> it is really ragged.

Michael,
What kind of a 'miss' is it? Does the engine stumble? Temporarily loose
power? Die?
When does it occur? Engine cold? Warm? Hot? All the time?
How long does it last? Does it go away?

We need a bit more info to get the guessing machine oiled.

> Questions:
> 1.  What is that slightly oily plug telling me?

Most likely that you have a leaking valve cover gasket.

> 2.  Did I miss something obvious?

You seam to have covered the spark part of the equation (short of taking
the spark plugs out, grounding them and turning the engine over to observe
the spark).
That takes car of the fire, how about fuel and air?
How is your fuel pump? When was the last time you replaced the fuel filter?
Consider hooking up a fuel pressure tester to see if a). your fuel pressure
regulator is working; b). injectors are not leaking too badly; c). pump is
working.
Than there is the air part and all the electrical gizmos that keep it in
check. Suspect and run Bentley checks on everything from the coolant temp
sensor to the ICV and the DME.

Let us know what you find.

HTH,
alex f

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