The lambda sensor on my 145QV was responding slowly according to the test rig at my local specialist. This was not enough to cause the ECU warning light to come on, but was causing the car to run poorly.
If in doubt get it hooked up to a diagnostic rig to check (as long a you have a good specilaist who will do this for free!!).
My 146 failed the mot emmissions test due to a wire pulling out of the plug where it connects to the cars wiring loom. Even though its all safely tucked away in a box in the bulk head below the windscreen, this wire had pulled out enough to make the Lamda 'misfire.' Once reconnected, the sensor was functioning,the tester was satisfied and the owner happy.
Am I being presumptuous thinking my Lambda sensor could be the reason my Injector light comes on when the engine is switched on an hour or two since it's last drive? The engine runs poorly when the light is on but then picks up again when it switches itself off twenty'ish seconds later?
The garage who've spent several days trying to fix my injection light said they received no errors from the Lambda sensor but gave it a good clean.
See my post 'CAT' dated 24/04/03 my CAT went due to a faulty Lambda sensor. Nearly ruined the exhaust too, so I'd get it checked pretty sharpish if you want to avoid an expensive repair. My emmissions were very high, which gives a good clue.
I had my lambda sensor replaced 2 months ago after a long time trying to get a diagnosis!
Symptons were poor idling, engine was hunting and revs were dipping between 2000 ~ 3000 rpm. One thing that was very noticeable was when I was at traffic lights, the revs would dip so I would counter with the accelerator; however even with the accelerator depressed, the needle was jumping around erratically.
Hope you get your car sorted ... as it's a complete pain in the ar*e!