MKC

I have read numerous posts about Lambda failures and they all seem to include bad idling and possibly stalling when cold. I have a UK MY99 which suddenly started hunting on warm idle only (cold is great and rest of running is great too). Dropping from high revs makes the idling worse. It hunts up and down between 1000 and 200 to 500 revs (its a nice timely pulsing if that makes any difference).

I cleaned my ICV and its working. I tried two MAFs and its the same with both (fractionally different).

I wound my throttle cable nut up so it manually ticked over at 1050 revs which I presume eliminates the TPS and it works ok like this for a while but seems to learn its wound up and sorts itself out, lowering the revs and it stalls from high revs still again eventually.

Can a faulty Lambda only go wrong when the car is warm ?

Can it cause pulsing idle between 200 and 1000 revs etc as above ?

I am sure that taking it to Subaru will allow them to stick it on their diags system and check the voltages but I do not have the time in the day or at weekends to get them to do this and would rather change the sensor if people in the know suggest that it may cause my probs.

Thanks in advance. Colin