My car has what I can only describe as the 'hiccups' or a stammer!

Usually only occurs once or twice in a row, but today did it for about 5 seconds. Always while driving, no pattern to when or whether engine is cold or warm.

It feels like the car just hesitates for a fraction and then carries on. It occurs when cruising at constant speed or when accelerating and occasionally when lifting foot off accelerator.

Any one have any ideas?

My thoughts were that it feels line a belt slipping then catching (not sure any belt would cause this affect though) or possibly contamination in the fuel filter/pump. I use about 80-90% Texaco fuel and generally (but not exclusively) avoid supermarket fuel.

It's a PD 140 engine with 111k on the clock ('07) and about 5600 miles to next variable service.

Thanks in advance if anyone has any suggestions.

Run up behind it and shout BOO!

Sorry, it's the kid in me

Sounds like a sensor fault or other electronic wizardry

Tried shouting 'Boo!'

Car just looked at me as much to say 'WTF?'

Which sensor might be the cause of it do you think?

I've run a VCDS scan and nothing shows up. Is there a way to use VCDS with the engine running to get some meaningful diagnostics?

Might be something as simple as a blocked fuel filter. Do you know when it was last changed?

I was thinking fuel filter as it has been getting worse in the recent months (still only very occasional, but getting more noticeable and more frequent).

Fuel filter wasn't changed at last (minor) service (99k / June 2011) and is due to done on the next (major) one (in 6400 miles). Last fuel filter change is recorded as being at 80k / March 2010 (I am on variable / longlife service).

Sounds like a sensor fault or other electronic wizardry

Congratulations, you have achieved the rank of Main Dealer Master Technician.

I had a very similar fault with a focus diesel, turned out to be a damaged wiring loom between the common rail pressure sensor and the ecu. when there is no signal from the pressure sensor, the default value assumed is over pressure, so it was cutting back the supply of fuel to the rail, and hiccuping violently at times.

That sounds a little too dramatic for what I have...

Would this apply to PD engines anyway?

Congratulations, you have achieved the rank of Main Dealer Master Technician.

So, do I get a certificate?

I might fancy a career change

I would try a new fuel filter as its been sometime

Since last changed.

I've been reading up on fuel filter changes in Octavia's as they are different to the 'in line' filters I'm used to.

Any one have any top tips or hand hints for changing this type?

2 guides here for diesels, look at the one that relates to you , golf same engines

http://www.tdisport.com/Forum/viewtopic.php?t=7174

http://www.myturbodiesel.com/1000q/a5/2009-2010-VW-TDI-fuel-filter.htm

Update...

After eventually managing to find out which filter was fitted in my car (I got it right first time as I had the obvious one) and having had it in the car for almost a month, I feel that there is a difference.

I've not had the stammer / stutter / hiccups occur once yet. And it seems as if fuel economy is on the up again (about 3-4 mpg). And the car starts slightly better (it was just beginning to not catch immediately on turning the key).

All in, £17 and an hour well spent.

I change my fuel filter at every variable service, as well as pollen filter and air filter.

For the cost of these items, I can't see the point of not doing them. Ignore what the service schedule says and change all the filters at every service when you are on variable.

I'm with you on that now I've seen the state of the fuel filter after over two years since its last alleged change.

Mine will be done every year now.

It is an unfortunate characteristic of the PD fuel system design that they do tend to blacken their fuel filters quite quickly. The reason for this is reckoned to be tiny amounts of injector blow-by (ie soot) finding their way past the injectors and into the fuel system, and in moderate amounts this isn't considered to be a fault. This can't happen with a CR or a traditional rotary pump diesel setup and is a peculiarity of PD.

Personally I think the official fuel filter change intervals on these engines is ridiculous. They can get very black indeed in only 20k or less and can clog completely by 60k.

Thanks for that info Nick74. Quite interesting to read.

Considering mine has done around 40k since the last documented fuel filter change well over two years ago (variable service interval) I am inclined to agree with your comments about clogging so quickly.

I will be changing mine at each variable service interval now (around 14-16k miles).

when I had a Tipo and did higher milage I changed the oil filter twice a year and the fuel once a year 78,000 miles in 3 years and it never missed a beat

If that does not cure it. It is a possibility that its the maf. Get it fault read. If there are no faults codes replace the maf