Ford Fiesta Diesel failure on Emmissions test help

Can anyone help, we're rather stuck.
My mates Diesel Ford Fiesta is failing its emmissions test (MOT/Govt smog test) on emmissions. Any suggestions?.
We've changed the oil and put some injector cleaner in. Someone suggested a bit of fast motoring to clear it out. Wil that help. Is there some adjustment to the pump that can be made to help with this. Don't really want to take it in to get fixed if I can avoid it (big bucks, always is when its 'technical').
Cheers... Rob.
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Hiya Rob
Change the fuel filter as well. A quick blurt down the motorway never hurts either, well, as long as you don't get cought or blow it up!
m
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wrote:

Another thing to look for is air leaking into the fuel line upstream the pump. That will give you excess smoke. As will the timing being out. On Petrol vehicles changing the oil is a big factor for vehicles that do primarily short runs.
What year is the Fiesta? does it have common rail or is it an older model?
Here in N-America the standards are more stringent for the newer vehicles than the older ones.
I strongly recommend against putting any fiberglass filtering agent in the exhaust system to get you through the test as that will not fix any problems and might blow out during the test.
Best of luck.
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