Just ran Torque on 1.4Mpi and go the following;

TID:$02 CID:$01

Lean to Rich sensor threshold voltage

Min 2662

Current 167

It says this has failed test, but there are no error codes flagged up. There was a Temp sensor fault, which I've now replaced and cleared.

Any ideas? If there is anything of note it seems a bit running rough when started up - perhaps not as smooth as previously.

I think this in VAG term is "load cross check" or something, it is an additional adaptive tolerance that is available to correct fuelling under certain conditions. There are quite a few "parts or bits" that make up the total "value" that dictates the fuelling, like temperature,load,RPM etc The ECU will have an expected "window" for that additional "part or bit" and your engine is forcing this value to be outwith the expected "window" to provide the perfect mixture.

Reason for that I can't say, but if it was being forced to richen the mixture then some unmeasured air could be get into the inlet tract. If the opposite then the air being measured might be wrong, inaccurate.

A bit vague - sorry, check all the obvious things first.

Edited 27 February, 201313 yr by rum4mo

Just checked the mpg on car 1.4mpi and it came out at 29mpg for urban driving. Quite different from the 45mpg i got last year on a long motorway drive.

Still getting the same lean to rich message on the o2 sensor, and graphing it on Torque doesn't show a nice (or much varying) signal, there's a little movement when I rev the car but nothing like the example sinusoid.

So could it be the o2 sensor faulty?

Coolant temp amongst other factors dictate fueling, depends if you have LTFT and STFT trims on this ECU.

For example upon first startup upto x degrees c you run a rich fueling condition, and like the old choke.

If your MPG is down one other questions is, does the car idling badly or feeling lumpy? - if yes then its likely you need to replace your lamda sensor/o2 sensor

Generally on WOT the o2 sensor is ignored where it refers to hardcoded fueling and ignition timing maps.