VVC very high CO on MOT

Hi,

just stuck my VVC in for an MOT and its failed on a very high CO, around 7%. Its a MEMS2J model, with the coilpack on the block, not on the head.

___ Actual ___ Limit

CO 6.94% 3.5% MAX FAIL

HC 307ppm 1200 MAX PASS



IDLE SPEED: PASS

SMOKE LEVEL: PASS



I'm just trying to work out what to start replacing first.



Things that have already been done:

I put a new lambda sensor (think it was NGK) on it before it was laid up for a year. Can these things corrode as the downpipe was left off for most of that time?

Magnecor leads are fairly new

New spark plugs last week



I stuck my multimeter on the air temp sensor and it read 600ohms, i'm guessing if it failed it'd be open circuit.

The cooling fan kicks in when it gets hot, so i'm guessing that works (although it might be reading wrong, i've no idea)



I'm thinking that the cat alone won't cause a reading that high, it passed an MOT with that cat about 1000 miles ago, although it has been left disconnected outside for about a year.



The idle sometimes seems to sit slightly higher than normal, and a blip of the throttle brings it down again. It isn't the throttle body sticking, it seems to be throttle position sensor related. Could that cause high CO?

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