Micra K11 emissions MOT fail-new cat time?

[fritzy]

Hi
My car (micra k11 1ltr) is refusing to pass the emissions test at mot. Originally I think this was down to bad soldering on the throttle body causing it to run super rich which I've attended to. However, I've since put cataclean through it and been for a blast on the motorway (waste of time and money) and checked for errors on the ECU-none shown, but it still fails the CO test.
So... should I change the catalytic converter or is there anything I might have overlooked? I think that because it was running with the mass air flow sensor problem for so long that may have trashed the cat. any thoughts would be most welcome, thanks.
Fritzy

 

[pollyp]

check O2 sensor

 

[frank]

check O2 sensor

+1 the middle wire should be fluctuating at about .45v

 

[fritzy]

Thanks guys, I've done that, in fact that was my first thing. I changed it and have checked it. Anything else before I change the Cat?

 

[fritzy]

Correct me if I'm wrong. I checked for errors by shorting out the bottom left two pins on the diagnostics socket and turning on the ignition. I got 5 long and 5 short flashes which indicates everything is normal, right? then on starting the engine and revving to about 2,000 rpm the light goes on and off intermittently which I believe indicates the MAF sensor is working ok. now, is this a complete picture or do I need to get some sort of diagnostics tool or engineer to look at it more thoroughly?
I'm just not 100% convinced that a new cat will sort this out, and it looks like a pain to do as it's right on the manifold. Any input is once again most appreciated,
Cheers.

 

[pollyp]

during diagnostic mode II reving engine at 2k the eng light flashing on off indicates the O2 sensing lean/rich afr. it should switch back forth bout twice a sec. flashing less frequently may indicate old sluggish O2 response.

also check spark gap and timing

 

[fritzy]

Thanks. Yeah mine flashes a lot less frequently than that. The flashing light is detecting the MAF sensor info though, right? As opposed to the O2 sensor on the manifold?

 

[pollyp]

no the light On indicates O2 mixture lean