I know the lambda sensor controls fueling, but that is all I know.
Can someone give me some more info, regarding when it controls, is it under full/part/no throttle. If it fails does your can run rich or lean, if so again full/part/no throttle.
Many thanks Keith. Sti v5

Someone must know.

I am no expert....but I'll have a go. The ECU runs open loop and closed loop fuelling, one references the lambda sensor and the other doesn't. When at WOT the ECU doesn't use the lamdba, when cruising at, say 2500rpm light throttle (no boost) then it does use the lambda sensor. However the ECU's interpretation of WOT isn't purely based on the TPS (or foot to the floor), it takes into account rpm, boost etc and decides itself when to run rich.

When at idle and non WOT conditions it uses the lambda, however on first startup the sensor needs a few minutes to warm up, what the ECU does then I do not know.

I assume the sensor would fail safe - i.e. as if it hasn't warmed up.

Hope this helps, experts please correct me if I'm wrong :)

Justin

Thanks Jay, So am I right in thinking that it only comes into play or part and no throttle? Also if it fails does it run on the rich side?
Keith

Yes, IMO the way you're thinking is right :) However I don't know for sure.