Hi folks,

Trying to get to the bottom of why my friend's Fiesta has managed to fail the MOT on emissions.

It's a 2014 1.6 TDCi with approx 80,000 miles on it. Full service history and appears to be fairly well looked after. Just been serviced, about a month ago.

The big issue is that it failed the MOT last week for emissions, both on visible smoke and the quantity, plate value on it is 0.62 and it was spewing out 1.5 at the lowest. Visible smoke is a fail anyway for DPF equipped cars.

Troubleshooting steps so far:

Italian tune-up

It's using good quality fuel, not supermarket stuff

Miller's Ecomax in regular use in it

Serviced recently, had a new fuel filter as well, just in case as that hadn't been changed with the service.

We've hooked it up to Forscan, no fault codes were logged.

MAF was reading slightly funny, we've replaced it but with the same symptoms, drivability of the car has been improved though

Car has completed a forced DPF regen with no problems

Intake has been cleaned, and wasn't particularly gunked up.

No apparent boost leaks either.

Has anyone got any idea what I should be looking at next? MPG is good so I'm not suspecting an injection fault but the car needs to get back on the road really.

Not overly helpful comment : as far as I can tell, if you removed the sticker on the door post with 0.62 on it and took it to a different mot garage then the default value of 1.5 should be used. But that does not get round the visible smoke issue. The emission value on the plate has only be used for mot tests since 20 may 2018. 

More debate on this point today on Mondeo forum under Mot failure - adcice required.