O2 sensor fault?

[ex-Chinese Dave]

Yesterday my 172 Cup started to feel rough under 2k rpm, almost like a misfire, but no lights came on the dash. The car was tuned at EFI a few months ago and has run perfectly since then, until yesterday morning (1am). I drove the car to Birchdown yesterday (to have a gearbox fitted) at 6am and it ran fine but I asked them to have a look at this problem. They plugged it in and it showed no fault codes at all. When Steve did the road test he said one time under 2k rpm he felt something that he thought was the engine being cut. He suggested that it could be an O2 sensor on the way out. The engine is standard on 128k and the exhaust is standard. Any ideas as to what it could be, and if it is an O2 sensor which do I get etc?

 

[JamesBryan]

The Birchdown lads will be able to sort it, if it's still with them.

Would need to graph the pre-cat sensor to see if it's switching fast enough.

 

[ex-Chinese Dave]

I've got the car back now as it was just a day trip to Birchdown.

 

[JamesBryan]

Ahh, in that case you'll need to get it logged.

I can do it if you're ever near Warrington for a while.

Does it do it from cold and hot?

 

[ex-Chinese Dave]

Thanks for the offer.
From hot but it only did it from yesterday. The drive back was fine and when I left the car to cool down last night it was fine again.