1996 850 Running Rich

I have a 1996 850 Volvo with 38K miles. I just bought it a few months
ago. I had code 422 which I researched to the 2 O2 sensors not agreeing
with one another. I replaced the front O2 sensor and now the car runs
rich. I do not get code 422 anymore. I see black smoke coming out the
exhaust. I do not get code P172 (running rich) as of yet. I replaced
the O2 sensor with a Bosch Volvo replacement ($150). I disconnected the
battery for several hours and connected it again. Do you need to
replace both sensors at the same time? Any other ideas?

Regards, Bill Bell

 

I do not how much if any bearing this will have on your problem but it
may give you something to think about and may save you money. I am
presuming that you bought the sensor and self fitted it?.

I have a V70 T5 and after a service plus a top engine mount change it
went like a rocket<g>. However the performance was due to massive
over-fuelling due to the fact that the mechanic left the clamp holding
the turbo inlet pipe completely undone. The extra air sucked in
through the loose outlet pipe from the air box fooled the sensors into
pumping about 50% extra fuel. The consequence was black smoke from
running too rich and a code was thrown when the first O2 sensor gunked
up with soot etc.

The garage warranted their work and a new sensor was fitted but here
is where you may have a problem. The new sensor, and they were the
only ones available are re-designed and need the latest software
download to work properly. Although I had a sensor fitted in a
different model vehicle it may be that Volvo have changed the
parameters retrospectively and the new may not communicate correctly
with the old without software changes. My software was up to date as
it was re-loaded in the last six months.

It only took 120 miles of a loose turbo pipe to finish off my O2
sensor and I do hope that your $150 lasts longer than that.

Liam