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Re: Problem with '91 Eddie Bauer
It's not surprising that the engine is running rich -- the computer thinks
it's lean, so it keeps throwing more and more fuel at it, until reaching the
end of the trim adjustment. Sounds like you have a bad oxygen sensor on the
left bank, or (much more likely), the sensor is unplugged, disconnected from
the computer, or shorted to ground. Oxygen sensors rarely fail, but your
rebuilder might have damaged it by using silicone sealants, or, perhaps,
coolant got into the exhaust.
Have you or your mechanic run the on-demand diagnostic (KOEO, KOER)? On a
'91 the only tool needed for that is a paper clip. Those should confirm the
always-lean reading.
One way to start troubleshooting this condition may be to unplug the sensor
in question, hook up a DVM to it, and force a rich condition (unplugging the
coolant temperature sensor typically does the trick). If you see black smoke
billowing and the sensor is still at 0V, you have a bad sensor. Otherwise
check if the harness is intact and not shorted to ground somewhere.
"John D. Goulden" <jgoulden@okcu.edu> wrote in message
news:dsam510gjl@news2.newsguy.com...
> '91 Eddie Bauer 4x4 4.0L, 220K but with engine rebuild about 10K ago.
> Rebuilder is not my regular mechanic.
>
> This has been driving me (and my mechanic) crazy. Check engine light comes
> on after about 10 minutes; codes are EGO not switching, left bank lean
(hope
> those make sense, going by memory of what they told me here). However,
other
> indicators are that the engine is running rich: poor mileage (12 mpg
instead
> of my usual 16 in mixed driving; black soot in tailpipe).
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