Smog test fail, Catalytic convertor or what?? Options

[bigredcelica]

Hi,
I have 1994 St202 Celi with a 3S GE injun with 90K miles. I have recently got a NCT test (Irish road worthiness test) which includes a similar test to the smog emmissions test. My low idle (1000 revs) showed fine but my high idle (2750 revs) came in over spec. The standard is 0.3 where my results were 0.4 These are ppm results, or a multiple of, for CO or Carbon Monoxide.

I brought this to a garage where the emmissions showed results of 0.005 for high idle but as soon as the revs were dropped the result shot up massively for a few seconds. He tells me that the cat is gone (nine lives my ass). Is he right? I wouldn't be very trustworthy of his business and need verification before buying. I don't partiucularly want to go down the road of adding Ethynol or such like to the fuel just to pass - I would rather get the car as it should be.

Any thoughts?

[bigredcelica]

GeEkBoY - you have me curious. My hydrocarbons were excellent. What does the O2 sensor do? I have just got a cat from a MR2 that with a bit of modification should fit my celi. This has an O2 sensor attached. I plan to change it out this weekend but if a sensor can do this then this may be a quicker and cheaper solution.

Considering my car has 90K on the clock I might be as well changing out the cat but curiosity is getting the better of me as to how a sensor can affect the emmissions.

Thanks for all the replys. I intend in getting premium fuel next time with a bottle of emmission rerducing fluid - hope all goes well!

BIGREDCELICA