I would be interested in the answer too. My MOTs are done at ATS and they no longer automatically provide the emissions report on an MOT pass. I find the report useful as a guide to general engine health, not so much CO but certainly Hydrocarbon. The MOT pass of 200ppm is way too high for a healthy engine running correctly; it has been a long time since I have seen figures as high as Johnos, something very obviously wrong with that car, I’m sorry to say. Hydrocarbon is unburnt fuel at the crudest level, so that car must be using a lot of petrol if oil level not dropping.
My 1998 NB at 126,0000 miles is still on the original catalytic convertor. The cat has to be really hot to pass the emissions. I believe there are two menus on the emissions tester and it is important the tester uses the correct one. It is also crucial to ensure that there are no exhaust leaks as this affects the lambda reading.
NB’s do seem to be tricky to get the emissions compliant.
I believe they are not obligated to issue a print out if it’s a pass but must give out a copy if it’s a fail.
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Spot on Reggie - that was the advice the MOT tester gave me for my NB
Do we have anything from the original poster on what the problem actually was ?
Success, the problem turned out to be spark plugs replaced the plugs and she’s running fine now. 
Wrong spark plugs fitted or a duff set?
I think they must have been duff plugs they had only done 11,000 miles and were Denso plugs and was told that they were super plugs sadly not the case.
Could’ve been counterfeits, there’s plenty around, NGK, Champion etc.
Didn’t know that at a cost of £60 its a good earner.
Could have even been the 2.0 plugs as the 1.8 takes different shorter thread plugs…
their counterfeiting spark plugs now!!!
OH FFS.
so i guess i need to stick to very reputable parts places for parts now!
Been going on for ages, there is a Denso website dedicated to the id of counterfeit plugs against original Denso. In this case I think the wrong type of plug may have been supplied and fitted, an easy mistake for
those who just think all mx5 nc’s are the same engine.
Ps, thanks for the reply so often we never know what the problem and solution actually was!
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If plugs were the cause of this huge hydrocarbon output, that car must have been running very rough with a lot of misfires. Perhaps it was only running on three cylinders?
I don’t use the car in the winter but it seem to run ok when started little bit of smoke on start up but it had been standing for al most 5 months.
Just dug out the form for my 2006 at last MOT Fast Idle CO 0.004, HC 8.
well, my 5 past its MOT yesterday, straight through, no advisory’s.
the emissions results are meaningless to me, so maybe you guys can tell me if thhese are good or bad!
You have a zero reading for CO% and 5ppm for hydrocarbon. These are at the very bottom end of the range as you can see from the limits. As a comparison my 1978 Corvette with no emission equipment at all would return about 0.1% CO and around 125ppm hydrocarbon. Your car is operating fine just keep a check on next year’s results which should be very similar if all is still OK.
The MOT limits are set very generously and most cars in reasonable condition should be able to pass with no problem.
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Last time I took my nd for mot the tester had to rev the car to pass the emission test. He asked me if I used supermarket petrol, I told him Asda. He advised me to give the car a good spin at the next mot to burn off residue. I’m due mot next month so I’m going to give it a good run up the motor way on my way to mot. Let me see what happens.
The answer is simple, use Shell V-Power. My ND was producing virtually fresh air when tested recently!
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