OK, thread for advanced techs. New to me 03 Disco - had a dead 02 sensor when I got in on the passenger side - drivers side cycles fine, passenger side reads zero or .1 volts.

Replaced 02 sensor. New sensor reads steady .9 volts at idle after warmup, but you can see the ecm trying to cycle it when driving - never goes below about .5 volts except on DFCO, goes to zero then. Fuel trim on that bank at -25%, Fuel trim on drivers bank around 3% positive. Inducing major vacuum leak at idle sends it right back to zero volts.

So I am thinking leaking injector or dead plug right? Pulled all four plugs, can't see any difference in them - all four white/tan electrodes

Pics attached of plugs.

I'm baffled...ideas?

P

 

Bad connector? Bad wiring harness? Have you tried thoroughly cleaning the connectors with electrical contact cleaner?

 

Front sensors will cycle .0 to .9 volts.

Back sensors will remain constant voltage at about .24V or so ONLY
when you are under a lot of load up a hill and the sensors are bloody hot.

If your front sensor is not cycling then put in the correct Bosch Sensor.
Not some China sensor or some NTK junk.

If you have put in a new Bosch sensor then undo the connector - looks for bent pins or cracks or that you just did not plug the connector in all the way.

the connector is way way up there.

 

Take a look at http://jeffreyfall.com/landrover

The sensor part of my post is the same for a D2.

 

Update, got up this morning and all of sudden it's working? Not sure why it didn't last night but I guess it doesn't matter why, just that it is...

 

Don't worry.
It will quit working soon enough.
replace the front O2 sensors.

 

that was the point of the thread, they are new o2 sensors.

 

Extinct, in the future, you will get more help if you give specific information for us to work with like, year, model, mileage, fault codes.
Let us know if you have any more problems.

 

New update - no more codes for O2 sensor, but now I have recurring misfire issue. Conditions:

1. Most common code is 0307, sometimes accompanied by 0305 or 0302 (03 is misfire and following two numbers are cylinder number) or 1300 (multiple misfire).
2. Only occurs one first start in the morning - all other subsequent starts throughout the day do not set code (I clear the code almost immediately after the first 2 minutes of running and it does not come back).
3. Replaced #7 sparkplug thinking maybe it was a cracked insulator that closes up when insulator expands due to temperatures.

130k, year in first post, posted in DII section so obviously a DII.

Anyone else ever have this?

 

The ECM doesn't cycle the rich/lean part of the sensor, the sensor makes that voltage itself. So if you have a good sensor and it's stuck rich like that, it's really running rich. The ECM only directly runs the heater circuit.

You may want to take a good look at the plug wires if they aren't new. You can run it at night and mist them with water. If there are any wires shorting out, you'll see sparks.

If this misfire ONLY happens after first startup of the day, there is a possibility that the head gasket or intake manifold gasket is leaking slowly into one or more cylinders making it misfire until it burns off the coolant. Usually with a leak like this, they are so small that you won't immediately lose a noticeable amount of coolant.
I hope it turns out to be something easy and not a head gasket!
Good luck.