On Mon, 8 Jun 1998, Mark McCulley wrote:

> Following a recent tuneup (plugs, rotor, cap) and O2 sensor change my
> mileage has dropped almost 3mpg (from ~18 to ~15). I just replaced parts and
> did not change the timing or CO settings. I'm using the same plugs as before
> (W7DTC) and the engine seems to run just fine. The new O2 sensor was the
> generic Bosch 3-wire sensor that I spliced onto the old connector. I'm at a
> loss to explain this--I've been through 3 tanks of gas so it's not just an
> anomoly in measuring mpg. Could the new O2 sensor be causing the FI to run
> richer somehow?

I guess the "curve" of voltage output on an O2 sensor changes with age, so
if the CO was adjusted using the old O2 sensor, then the new O2 sensor,
giving a differnt voltage for the same CO level, would have some affect.
However, I doubt if it would be this dramatic.

My first thought would be that the splice (or the new O2 sensor itself)
was not good.  Check the output of the new O2 sensor with a volt meter.

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