At present, they can't 'test' in the MOT for the DPF working correctly, so they can't check if it has been removed.

If that changes (and it probably will, at some point, something similar to the smoke test), then your car will fail the test, and it will cost you £1000+ to get a new DPF fitted. In addition, if you sell the car, knowing that it has had the DPF removed, and you fail to tell the purchaser, then you will have committed the criminal offence of fraud.

Almost impossible to diagnose this online correctly.

If it was mine i'd ask around for a good VW specialist, and a dedicated Diesel workshops, both by recommendation, nip the car into the one that gets the best praise, or both if still unsure.

At present, they can't 'test' in the MOT for the DPF working correctly, so they can't check if it has been removed

Well that is half correct.

They cannot test if the DPF is working correctly

BUT

they can visually check to see if a DPF is present. If its ovioulsy missing or has clearly been tanmpered with to remove the internals or sensors are obviously not installed correctly you will fail and to get a pass you will have to get a new DPF installed and the car software updated. As of February this year (2014) this has been part of the MOT.

Will not be cheap to get sorted either way but why do it twice.

Thanks everyone for the answers.

I have found a VW specialist and I'm taking the car there today. Hopefully the matter will get sorted without paying a fortune .

I'll write an update after I have come back.

I know that the intended design life of a modern car can be as little as three years.

Just checked the date after reading that comment and its not April 1st.

We keep our cars 5 years on average. My last car was a BMW 118D, the one that breaks its cam chain and has a million other problems. In 5 1/2 years the only part I bought was a front spring. It was correctly serviced by BMW from new.

Wifes previous car was a Focus 1.6 TDCi, the one that has huge turbo and a million other issues. After 5 years it was running prefectly and the chap who bought it still has it 4 years on. Still running perfectly. Was serviced correctly form new.

We have a 7 year old Micra, the one that has a million issues according to most web sites. Been serviced correctly form new and the only new parts fitted so far have been one wiper blade and a front spring.

Spot the comment that is consistent here, all the cars have been serviced correctly from new. Most cars with major issues that feature on here and other sites have either missed services or been serviced using cheap parts and incorrect lubricants to save a few pounds.

When I was in my teens the cars I bought were about 10 years old, mechanically almost knackered and bodily rusted out. Now look round, 10 year old cars are all in good condition and still run perfectly. A colleague of mine recently sold a 10 year old Rover with nothing wrong with it mechanically or bodily

There are some features of modern cars I would happilly live without, electric handbrakes are just one, but I am far happier in my modern climate controlled, ABS braked, fuel injected, air bagged, disc braked, etc etc car than I would be driving a 3 year old rusted out unreliable Escort in the 70's.

Back to the OP. Diesel engines produce particulate matter which includes carbon (soot) and metal, as well as gasses. Not all of the PM can be broken down by the regeneration process, and so over time the DPF will become so blocked that a replacement is the only option. The more short journeys you do the quicker the DPF will become blocked. They can be professionally cleaned but this is a specialist job, and even then it will eventually need replacing. The regeneration process works by the ECM adding a post injection stage to inject fuel just before BDC, so that the fuel ignites and burns inside the exhaust. This increased temperature burns off some of the PM so it can then pass through the filter. This procedure will only be activated under certain driving conditions controlled by the ECM. The driver cannot make a regeneration happen, other than to be driving in a manner in which the ECM will commence the process.

If your motorway MPG is poor the problem could be that the ECM is continuously trying to regenerate the DPF. This could be because the DPF has become so blocked with PM that cannot be removed, and in this case a new one will be required, or the pressure differential sensor which measures the pressure difference either side of the DPF could be faulty. Check the pipes from the DPF to the pressure differential sensor to make sure they aren't split or blocked, which would lead the ECM to think that the DPF is blocked and needs a regeneration.