So the problem started after a 2 hours trip to Orlando. When I returned home, the RPM started to bounce between 500 RPM too 1500 RPM while idle.

Here's the thing. The issue stops or is not as bad when the AC is ON which has me confused. Usually in other cases the issue is more problematic when the AC is OFF.

The CEL is on. The front Oxygen sensors is reading too rich and lean. The rear is not responding at all. It is my understanding that the rear Oxygen sensors are to check the Cat converters.

I've read other forums with similar problem but have all hit a dead end with no solution. Ive read that changing The Oxygen sensors doesnt fix the problem. Anybody have a clue? Could it be as simple as cleaning the Mass Air Flow or something? I would like to drive my car more than just around town. I'm a bit desperate at this point. Pls help. Pls.

 

to the forum


It's a 1998 what ??

 

S70 Non turbo

 

Bank 1 Sensor 1 reads too rich and too lean, like a heart monitor

Bank 1 Sensor 2 reads 0 voltage.

 

You posted in the area to report or discuss issues with the forum itself, not cars.

 

My mistake. I Vol-vow never to do it again.
I guess it was a Sensor-tive situation.
But advice? I'm about to replace the B1S1 Oxygen Sensor. But if someone says "that's not the issue" let me know.

 

before you swap the sensor, did you inspect the vacuum lines/tees/elbows and intakes for leaks?

what can happen is a vacuum leak can force the o2 sensor to compensate to the point it goes "out of range" and throws the code. Do you have other driveability issues - ie power seems off, bad gas mileage? If not then it may be another component throwing off the ECU (which blames the O2 sensor) - such as your MAF, MAP, idle air valve, dirty intake etc. So after checking vacuum leaks, you can do a quick inspect of the MAF and idle valve and intake (free or worst case is a $6 of CRC MAF cleaner). I'd probably also do the (free again) rubber glove test to see if the PCV system is working properly too. You can also do some tests on the sensor itself (ie checking voltages/resistance) - there's two elements to an O2 sensor - the heater (lead should have a fixed voltage) and the sensor (variable voltage) - both should also have baseline resistance values. At a minimum I'd check vacuum lines and see how clean the MAF is...