O2 sensor

[400brad]

I have read a lot about O2 sensors lately.
How do you know when it is time to change it?

My XJ has 170K on it now and as far as I am aware the sensor has not been replaced yet.

I have read that it will become heavy on fuel if the sensor is playing up. This is not the case yet. I am getting about 12.5l/100 as an average.

I had the cat converter replaced about 10 000kms ago and it is starting to rattle again but only under hard acceleration. I have been told this is due to the motor being out of tune. Could the O2 sensor be the culprit?

The rattle isn't pinging is it? Pretty common from what I've read, and only stops with premium fuel, or sometimes a snorkel. I get it pushing up a hill or towing the camper. A "tune" won't fix it.

[junglejuice]

When I changed my O2 sensor mine stopped pinging altogether but as it turns out my economy has tuned to crap....
Try running it on premium for a while and see if that helps the pinging.

[Rodgebone]

the O2s should have been done about 70K ago

[Grant]

I have never ran on Premium and it has never pinged, I changed my O2 sensors at 250,000 K and fuel economy was absolute crap since replacing both sensors and re setting computer economy has dropped to 11.5 litres per 100 K (that is on a trip from Adelaide to Beachport (SA) towing my 16 ft caravan home from Beachport to Avoca (vic) averaged out at 15 litres per 100 K

[TrainBoy]

Grant, how did you reset the computer?
I am about to replace my O2 Sensor, and wasn't sure what to do about the computer.

[94xjeep]

Hi brad,
first make sure that your manifold is not cracked as this can give the o2 a reading of being lean due to the extra oxegen getting into the manifold.They all crack(genuine manifold) above the o2 sensor ecu gives the engine a little more fuel and bingo the cat melts due to the extra fuel burning inside.
DO NOT cut and solder the wires on o2 sensor loom.First thing is that the wires are stainless and it does not solder properly.
The o2 sensor needs an outside source of oxygen to get a balance of whats outside to what the engine has passed freely through the exhaust.It needs a smaple.Altertude.This sample comes through the wires (very very small amount) via the plug were it plugs to the vehicle loom.SOLDERING them blocks them.Bad signal.
I got mine from America and they were about $90 bucks each and are made by NTK which is the same as the genuine one.READ THE PART NUMBER on your sensor and get the same one. Dont stuff around with them just screw in and plug in.
They operate on a small voltage that they produce from the oxegen in the exhaust. 0.1 to 0.8 up down up down as the fuel is trimed.
4 wire is a heated type.If the heater is U/S then it will not reach operating temp quickly and will bring the engine light on.Ecu does a count down from start up and if does not see operation it cant go into closed loop.
BEN