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850 woes 850 1996

posted by  someone claiming to be bl on  Sun Apr 25 08:52 CST 2004 [RELATED]

Thanks for the input guys! Some more info:

All started with a CEL in Feb. Fault code (Alex Peper software) "Voltage low O2 sensor one, bank one". The rear sensor was replaced by prior owner in Oct. 03. I though no big deal, replaced the front sensor and reset the light. The car was at about 100K.

Thought all was well but then the mileage began to nosedive from 25 mpg hwy down to 10! Blowing black smoke, idleing like crap etc. CEL back on with a fault code of "Rich". WOW! As if I didn't know that.

I pulled both O2 sensors and checked each with a torch. They both reacted with a voltage of ~ .55v or so so they were at least working. Took the car in. THey found a vacuum leak at a manifold elbow and thought that was it. It did run better but the CEL came back on in about a week and the mileage was still down. Still reading "RICH". Back in.

They changed the FPR and John (mechanic) kept the car three days driving it back and forth home, all over town going for parts etc etc. No problems. Ran fine and the light stayed off. We had it back a week and the CEL came back on, running rough as hell and blowing black smoke etc etc. Back in.

Analyzer showed a fault in the FI computer which they'd never seen on an 850. Swapped one from another 850 however and presto, everything appeared normal. Fine for another week and then the CEL back on. Now two codes showing "Voltage low both O2 sensors". I checked each one the other night by unplugging the connectors one at a time and measuring the voltage off the black wire with the engine idleing:

Front sensor: Voltage rose slowly (took about 4 mins) and bounced around at ~.65v.

Rear sensor: no significant voltage detected. I read 0.00 to 0.03v. When I remove the sensor and let it dangle, heat the tip with a torch, I read the above voltage so it is working and the wire seems intact. Question: I know this has destroyed the CC. Can a ruined cat be preventing the rear o2 sensor from heating up or functing? Is this likely an O2 sensor problem?

Know I'm not great at explaining anything. Does this help?

Yea, I hate to send a car to Goodwill too ut they're hard to get anything for with a CEL shining on the dash.

Many thanks!

bruce






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