Hi All,

My J-pipe was rotten and I was hoping it would
last a bit longer than it did.  When it fell off,
the exhaust waent going right out without passing
the oxygen sensor.  The van ran really rich when
in closed loop, but ran fine when cold.  When warm,
it would misfire at idle and part throttle.  At full
throttle (open loop again) the engine fired on all
cylinders.

I didn't realize the oxygen sensor had such a large
impact on the mixture.  On vehicles of this vintage
(mine's an '87) I thought it was just used to fine
tune the mixture.   I was surprised the engine
ran so rich that it misfired.  I suspect something
else might be wrong, to make the mixture even
richer, like a busted fuel pressure regulator.

Anyone have an opinion?  Anyone ever unplug
their oxygen sensor or have a bad one?  How
did the van behave?

--tabe johnson
xtabe@yahoo.com

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