Three Problems or One Big One!?

I have a P38 4.0ltr manual P-reg range rover, she has been going very well since I got her but.....

There are three issues I have found at the moment they might be linked or not this is the question and how to solve them all...

1.) The emissions have are right up (although think they always were!) I am thinking first stop is Lombard sensor...

2.) The engine intermittently keeps playing up 8 times out of 10 she is good as gold and fine and then she sometimes keeps, stalling, the revs just running right down when idling or taking out of gear and stalling or sitting at 500 revs and not sounding at all healthy and not picking up immediately when I put my foot down on the accelerator but fine once going...

3.) I am loosing oil at a rather rapid rate, although no signs in engine bay or anywhere on the car of splatter or leaks have already replaced the Oil Pump, flushed the engine and replaced all gaskets, then replaced core plug into oil gallery and the rear main oil seals and T-Seals...... Although I think I can smell oil I think when the air con is turned right up...

Any help to one of the above points or all three is much appreciated.

Thanks in advance...

Ben

First it is a Lambda Sensor!!

Possible, but the loss of oil is the main issue, the emissions are up because it is no doubt burning oil in the combustion chambers...my thoughts are head gasket has gone or Piston rings worn, if there are no external leaks...it has to be going somewhere....

Is there blue smoke from the exhaust?

Is there traces of water in the oil or oil in the eater?

I would get a compression check done and see if there is a lack of compression in one of more cylinders....then drop a tad of oil into the cylinder(s) that are running low compression and if the compression increases...it is more than likely piston rings, if the compression is still low, suspect Head Gasket or valves.

Get it on diagnostics to check the Lambda and MAF sensors for correct operation....but my thoughts are with the oil loss being the main culprit of your woes!