[bmw] 750iL catalyst opinion...

["Rick Marz" <rick@xxxxxxxxxxxx>]

I have a high mileage 1991 750iL (227K miles) that just failed the California
Smog II emission test.  This car was always well within emission limits - 10
to 20% of max - but with the new Smog II dyno test it failed the low speed
(15mph test) on both HC ppm; 134 vs the limit of 100, and NO ppm; 880 vs the
740 limit.  It passed the 25 mph test  within limits.  Not way off the scale,
but certainly failing.  The inspection station suggested that perhaps the
catalytic converters needed replacement.  I feel that 227K miles is certainly
a lot to expect out of the original converters, but would appreciate the
opinion of this board as to whether to invest $800 in new converters and
re-submit to the test, or if something else might be suspect.  The car
recently had the Inspection II (within the last 4000 miles) which replaced
plugs, filters etc, so should be well within tune-up specs.

Question two, if the catalytics are replaced, should the oxygen sensors be
replaced as well.  I think they have only been replaced once in the 227K
miles.

Appreciate any comments you can provide, this has always been a very
knowledgeable board.  What would you do?

Rick Marz
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