Hello,

I was wondering how many oxygen sensors are there on a 1995 xj6 and what are their locations?

Thanks

 

If you're in the USA...or any other country with "OBD II" engine management....you'll have 4 oxygen sensors. Otherwise, you'll have 2.

You'll see the sensors in the pipes just below the exhaust manifolds.

Cheers
DD

 

Hi all I have an AUS delivered Dailmer X300 xj16 4.0 N/A that appears to only have 2 x O2 sensors but also has OBD2 (to a degree?) does anyone know what the O2 sensors are marked as and whether this means that we have a different ECU ?
What do the O2 sensors actually do on this car - are they controlling fuel trim like the upstream O2 sensors on a 4 sensor car? Does this mean that the ECU is reading the downstream sensors as if they were upstream. Note AUS cars also do not have EGR valves also so much less pollution control on these cars.

All of this realtes to me having a -85.2 LTFT suggesting that I am running very rich - I wonder whether the Fuel Regulator has failed therefore allowing full fuel pressure to injectors and hence rich running then being controlled by the O2 sensors ?? Thanks Matt I have changed the following already, TPS, Throttle Body, Air Intake Temp Senor, CrankShaft Sensor, Coolent Temp Sensor and shortly Thermostat. Car runs well whenb cold but stalls regularly at random times when warm. I am working through all electrics - all relays and fuses changes, cleaned +ve teminals and battery terminals, cleaned all sensors contacts. Anyone got any thoughts ?

 

One thing that is common on these cars is the exhaust manifold crack. That allows extra air into the exhaust, which the O2 sensors read as lean fuelling and add fuel.

I'd start by removing the head shield over the exhaust and if there is a crack you can often see carbon staining, or some other sign on the manifold. Of the cars I have seen with cracks, it's almost always the front manifold for some reason.

Cast iron can be welded, but you need a skilled welder. The manifold needs to be preheated and you need a high nickel filler rod. A ordinary MIG welder won't work.

 

What does the OBD says for the o2 sensors? Do they switch to closed loop at all? OBD is generally not good for checking o2 sensor operation, you'd need a manual meter or an oscilloscope to check if they switch at all. OBD can give you a rough idea if they switch to closed loop and whether they cycle between 5V and 0V but it wont be accurate. They are not that expensive either and if they are original, you could just replace them.
There is also a possibility that someone connected them wrong, you could try switching plugs, see if that improves things.
I think only US cars have 4x o2 sensors, rest of the world and certainly UK, only has 2 sensors.

Meh, you can certainly weld x300 manifolds with a MIG without any issues. Simply start the car, run for a while with the heatshield off to heat up the manifolds, switch the car off, disconnect the battery and weld the cracks with a mig on full power with the manifolds still attached to the engine. I think I've welded 4 manifolds this way and never had any issues and no leaks afterwards. This will obviously be tricky with big cracks from underneath but mine were always cracked from the top and this repair worked fine every time. It might not be perfect, neither best option but it certainly works.

 

The O2 sensors on these cars are titania, they operate at a constant voltage and the resistance changes. It's different from the more common Zirconia type of sensor used in nearly every other car. For the 4 sensor system the ECU goes into closed loop, but the extra sensors are used to monitor the effectiveness of the catalyst. If they sensors above and below the cat read they same then the ECU knows the cat isn't working and will set a code.

 

No they don't. I have the LPG interface plugged in directly to my o2 sensors and a special diagnostic plug for troubleshooting, they certainly work in 0 to 5V range, just need a proper meter or oscilloscope to see the switching, especially on new o2 sensors, on old 'lazy' sensor its certainly easier to see it on normal digital multimeter or even obd.