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.
Failure of MOT Emissions test, what does it mean?
Sep 03, 2003
3 Replies
HC is unburnt fuel in the exhaust, so yes, misfiring can cause it.
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 !)
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.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required