MOT Emissions test failure

1 post

I've just failed an MOT due to emissions. I'm driving an N reg Ford Fiesta 1.1. It only has 46000 miles on the clock but the engine is burning oil. It also passed an MOT last year, though that could mean anything

The results were as follows:

Fast Idle Test:
RPM Okay
CO: 2.30% (should be < = 0.3%)
HC: 426 ppm (should be < = 200 ppm)
Lambda: 0.94 (should be 0.95-1.09)

Second Fast Idle Test:
RPM Okay
CO: 4.83%
HC: 482 ppm
Lambda: 0.87

Natural Idle Test: okay

As you can see, it's out by quite a lot. The mechanic suggested that changing the Catalytic Converter and the Lambda Sensor might get it through, but he couldn't give me any more than a 'might', and I don't really want to gamble the money on that, since I don't have much of it. But I really don't want to get rid of it as the rest of the car is fine; emissions is literally the only thing it failed on. Plus I really don't want to be without a car, as I'll be needing it a lot in the near future.

I also remember that the oil filter hasn't been changed at all since I bought it (and god only knows how long before that!), so I thought maybe that might help, though I'm wondering why the mechanic didn't mention that.

So, my question is, is it worth the gamble? How likely is it to fix the problem, or at least get it through one more MOT? Can you tell from the results if it's worth a try changing the cat converter and the oil filter, or is the engine simply buggered?