Failure of MOT Emissions test, what does it mean?

My vehicle just failed an MOT emissions test, on the Hydrocarbons, not the CO2. Apart from adjusting the fuel/air mixture, what can I do to ensure that it will pass when I get it re-tested. Would tuning it help? I think I was told that misfiring could be causing it. What is the high Hydrocarbon reading indicitive of? The vehicle in question is a 1986 Bedford CF2 Ambulance. Cheers.

Reply to
David Cullen
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HC is unburnt fuel in the exhaust, so yes, misfiring can cause it.

Reply to
Steve B

Make sure it is running on all cylinders, new plugs may be all that is needed. Other possibles are air leaks, dodgy HT components, I have even known a dodgy servo leak air in on one cylinder. If it won't run on all three at tickover then check compressions if possible. It may be possible to get it through a test by slightly raising the tickover speed.

MrCheerful (ps I also own a petrol CF !)

Reply to
MrCheerful

I presume you mean CO, since CO2 isn't tested?

It would be a help to know what both these readings are as the balance between them can give a clue as to the faults.

Reply to
Dave Plowman

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