Hi Folks,

This is my first post on here, sorry that its a question straight off, but I haven't had a real problem with this car before, have it since the 90's!!!

I'm looking for some advice on a 1995 Fiat Punto which failed the NCT/MOT on emissions with the following readings.

High Idle
Lambda 1.31 should be between 0.97 and 1.03 -- fail
CO 0.04% Not above 30% -- pass
HC 40 ppm Not above 200 ppm -- pass

So it only failed on the lambda.

I bought a cable and connected the ecu to my laptop.
No error codes were stored.

The live data for "Lambda Probe Correction" goes up and down on the graph
The live data for "Lambda Sensor in Closed Loop" graph also goes up and down when the engine is revved.

All tests pass, coils, injectors etc.

Car runs great, I'm at a loss with what todo with it next?
Any advice would be greatly appreciated.

try another oxygen sensor from a scrap yard, get the right one, the number of wires coming out can differ, [2 or 3??], It may be a cheap way out, worth a try.

Or the cat could be life expired. I got a new cat for my 1994 Punto 55 sent to Spain from a parts company on the web called OscarO, it came all the way from the Hebrides Islands in 10 days complete with a certificate stamped in Spanish saying it was EC EURO homologated, cost 60 euros !!.

Look for holes in the exhaust, otherwise could be sensors connected to the exhaust?

Thanks for the suggestions so far.

With such a high lambda reading it must be running very lean.

I took these pictures of the live data, do they look correct, is the sensor functioning correctly?

Pictures

high lambda reading only is very often just an inlet/exhaust leak. So obviously check for exhaust leaks but also vacuum leaks on the inlet side.
Remember the lambda reading on the test is taken from the machines probe at the end of the exhaust so a leak anywhere along it will give a false reading - it seems like everything is within limits and the lambda is working (or appears to be doing what its meant to do at least). So my money is on a leak in exhaust, or maybe vac leak as if you have a vac leak then you have more air going through the engine than the ecu thinks there is thus you get a high lambda reading, i.e. lean, to much air