On Sat, 11 Oct 1997, Blake C. Thornton wrote:

> What does a black sooty tail pipe mean and what do i do about it?
> (is it running too rich and do i need to lean the mixture?  How?)

Yes, a black, sooty tail pipe usually indicates a too-rich mixture, so
you need to lean the mixture.

However, first you need to determine WHY the car's running rich.  Since
there's feedback from the O2 sensor you should, in theory, never have
to adjust the mixture manually.

First, check the entire ignition setup to ensure everything's OK there.
Next, check the O2 sensor itself; it's the most likely suspect in a
"too-rich" situation.  If that doesn't do it, then suspect a leaky
injector.  You might also want to test the fuel pressure.  Finally, check
the air sensor; the spring that resists the movement of the air vane tends
to get "tired" over time and needs some adjustment.  (The procedure can be
found in the archives.)  You can set the correct mixture using a
voltmeter and the O2 sensor.  (Procedure also in archives.)

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Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
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