Check engine light was down stream o2 sensor. Does this have any impact on operation of the car?

Also, any experience replacing the bearing in the ac compressor? Reconnected it and it runs fine but the noise seems to right in front of the unit. Guy I bought from was sure it was the bearing and said he would replace it in a few weeks. Don't want to wait if I can do it now

Thx

 

O2 sensor has an impact of the car as it gives the feedback to the ECU which regulates the mixture. If the mixture is wrong (too much O2 per example) you can burn the valves from the cylinder head...If the mixture is too rich you can destroy the catalytic converter. Other than than it impacts on your mpg, and is of course a MOT fail

Bearing is not nice to do when the compressor is still fitted, you need to take out the magnetic clutch mechanism . Is this diagnose confirmed by someone who understands something about Volvo's ?

Also here is the "850 corner" you might want to check in the apropriate subforum ...

Cristian

 

Upstream does in fact feed info to the ECM and in doing so impacts the ECMs control of fuel delivery. It affects performance and fuel economy.

The downstream does not have anything to do with fuel control and only monitors if the converter is operating properly. If the downstream fails or there is a problem with the cat it shouldn't impact performance or fuel economy. As long as the cat isn't plugged that is.

 

Thx, any way to tell if it is plugged, car seems to run fine

 

When they start to plug it's most noticeable that at lower speeds it works fine, responds properly. Higher speeds, going down the freeway there's no power when you try to pass. The more air you try to flow the less power you get as it's restricting it. It gets worse and worse as it plugs more and starts hampering driveability at lower and lower speeds. It's kind of like having a governor and when you get to that point, no response from the gas pedal.

 

Great thx, don't seem to have a problem yet.