[chomerly]

I got the post CAT one from a salvage yard. The Pre-CAT was purchased as new from eBay.

Both worked fine for a time but after around half an hour the Lambda warning light came on.
In fact, this morning after getting back from work, i reset the error codes using my OBD2 device and the light stayed off.
I had been out to get some fuel as the missus said she needed to go out for a few hours, but that was called off last minute, and then i took my son to college for his enrolment day and on the way back the light came back on.
This was after a longer period of driving this time.
Roughly an hour.

One thing i should mention is that when the lambda lights are on, i get some light smoke coming from the exhaust.
When they are working, or at least appearing to be working, i get no smoke.
Also, i checked the oil today and it was way, way low on the dipstick.
So low that i'm surprised the oil warning light didn't flash up at some stage, but i know that is age specific vehicles with sensors to detect that kind of thing.

Now this had worried me further as i'm beginning to think valve seals or piston rings. But it doesn't explain why it only seems apparent when the lambda sensors are playing up.