Freezing diesel? Stuttering and juddering...

[ndicki]

It was -12° outside this morning, and during my drive to work - about 50 miles - the car was stuttering and juddering, especially when I needed a bit more power, say while going up a hill. It's normally very well behaved, and I hope this is nothing more than a bit of cold in the fuel system... No idea what sort of diesel it's got in it, as I fuelled up at the local supermarket (France) Could be anything, even if at this time of year, it's supposed to be treated.

Any ideas, anyone?

140 TDi Octy II, sleeps outside but not in the wind, and at the moment, I'm driving fairly gently anyway.

[fireftrm]

Well there you are - France. In the UK all diesel has winter additives to prevent it waxing up. -12'C shouldn't therefore have any effect here.

You need to enquire of your supplier and Skoda dealer as to the issue.

[rwbaldwin]

The problems with cold weather and diesel are the same everywhere, so I would expect it to be 'winter diesel'.

One thing it could be is the MAF, although I would have thought it would be a reluctance to go up hill rather than a stutter or judder. I would check the connection is OK by connecting/disconnecting it. The MAF is located on the pipe leading from the air filter. If this doesn't help, try running the car with the MAF disconnected. If the performance is better or no different then this would indicate a problem with the MAF.

Other potential causes would be failing fuel pump relay (IIRC 109), blocked injector or faulty temperature sensor.

[cheezemonkhai]

Have you had the fuel filter changed recently?

If not and there is a good amount of water in it then get it changed as this separates out (part of the filters job) and in very cold weather could freeze in the filter. This would make the flow inconsistent and could cause your problems.

HTH

[ndicki]

The fuel filter was changed a few weeks ago, in theory...

What's a MAF? This was definitely stuttering and juddering - and a reluctance, on occasion, to go up hill. But mainly stuttering and juddering.

Anyway, it's now a bit warmer - only -1°! - so I'm off home, hoping it'll be better by now... :confused:

[KenONeill]

Mass Air Flow sensor, which tells the ECU how much air the engine is flowing, and hence how much fuel is needed.

Your reported symptoms are typical of a duff MAF. Easy (well maybe not if you have to ask what it is) test is to disconnect it and see if the car runs better on the default fuel/air map.

[ndicki]

Well, I'm home, and she was her usual well-behaved self, with not a judder to be felt. I deliberately gave her a bit of stick up a couple of steep hills, and she went up like a lift.

Looks like it was the fuel... I'll chuck some injector cleaner in next time I fill her up, just to get any kak out that's still there.

A French colleague of mine agreed - he's had it before. So it looks as though French Winter diesel may or may not be treated. Welcome to the land where nothing is ever done quite right! :thumbdwn:

Thanks to everyone who's contributed! And the MAF may be a bit dodgy, but that's perhaps another story. She occasionally goes into "Limp home" mode when I try to get her up past 110-115 mph. But only when she's loaded. Empty, no probs. MAF? That's what a German Skoda/VW dealer suggested, except he called it the "Durchluftungsmesser". Sounds right.

[auroan]

Word of warning.... on PD engines VAG say do NOT use injector cleaner etc.

[Pud]

French diesel is good for -25°, sounds like you had water in it.

[_ZS_]

No fuel filter heater in Octavias then?

Seems there's one thing Vauxhall do properly then, and that's a heated filter on all diesels even in the UK. :lol:

[ndicki]

A friend who's a professional driver has just told me that they used to put additive in standard diesel up until a couple of years ago. Now they don't. So there's the explanation.

Thanks for the warning, auroan! I won't, then!

[KenONeill]

No fuel filter heater in Octavias then?

Seems there's one thing Vauxhall do properly then, and that's a heated filter on all diesels even in the UK. :lol:

If you take an infinite number of monkeys (or Vauxhall staff)...

[Gillywibble]

A friend who's a professional driver has just told me that they used to put additive in standard diesel up until a couple of years ago. Now they don't.

I'm very surprised at that given the massive difference in fuel economy this time of year.

[ndicki]

Don't ask me... But it doesn't surprise me at all. They're a clueless lot at the best of times. Look at the cars they build - good design, technically generally sound, built like junk. I had a Citroen once - never again!

[_ZS_]

What do you expect from "cheese eating surrender monkeys"?

[ndicki]

[Tech1e]

No fuel filter heater in Octavias then?

Seems there's one thing Vauxhall do properly then, and that's a heated filter on all diesels even in the UK. :lol:

TBH the fuel system gets that hot it requires a cooler on the return line, I dont think heating is really required on the PD, the high pressure involved are engough to heat the fuel up.

[Wavey_Davey]

Sounds like fuel filter waxing to me due to the cold weather. Your filter may be old, which only makes it more susceptible to any wax dropping out of the fuel.

French service stations can sell diesel with upto 7% biodiesel content, which also creates waxy precipitates at low T, so this may very well be why you're having a problem.In the UK, the biodiesel content is lower, up to 5%, but most of the oil majors don't put the maximum allowed in. Supermarkets do though- Tesco and Morrisons both use the full 5% allowance, often using animal fats and used kitchen oil in their biodiesel blends too because they are cheap, but they can often give waxing problems earlier than "cleaner" sources such as rapeseed oil.

All diesel in the EU is treated with cold flow additives in the winter. The diesel specifications (EN590) are regional for cold flow requirements- in the UK winter diesel is treated to -15°C CFPP (cold filter plugging point), exactly the same as in France. In Spain it is -10°C, and Germany it's -22°C. The only place they don't use additives in winter is Scandinavia, where the diesel is practically jet fuel anyway, and doesn't freeze until it gets down beolow -40°C.

Hope that helps!!! :tipspecs::tipspecs:

[Decron]

Seems there's one thing Vauxhall do properly then, and that's a heated filter on all diesels even in the UK. :lol:

Would that be all the Vauxhalls with Fiat engines in them.... The fuel heater is fitted to the fuel filter assembly and it does next to nothing anyway.

This week I have been using a 25% veg oil mix in mine and it's been fine down to -10c so I am inclined to think the problem isn't with the fuel but as mentioned it could be down to the fuel filter which will have water in it which will freeze. Also Vag do say no to injector cleaner, but if you go to most dealers they will happily sell you some and if you pay them even more they will even stick it in for you, best trick would be to get a bottle of Forte and a new filter, fill the filter up with the Forte put the new filter on and let it run. Bet you it solves the problem

Edited 9 January, 2009 by Decron

[Gillywibble]

Sounds like fuel filter waxing to me due to the cold weather.

Are there any other symptoms of fuel filter waxing other than stuttering and poor performance? Can it affect mpg?

[Wavey_Davey]

Are there any other symptoms of fuel filter waxing other than stuttering and poor performance? Can it affect mpg?

Waxing should only affect the vehicle at start-up, and for a period usually less than half an hour while the recirculation gets warm fuel back into the tank, and ultimately into the filter where it melts any accumulated wax. After the wax has cleared, you should not be getting poor fuel economy, or any other symptoms.

Anyone know what the fuel system layout is like for the octy? does recycled fuel go back through the filter, or straight into the tank? Is there a filter heater?

[_ZS_]

Would that be all the Vauxhalls with Fiat engines in them....

Yes, and the Isuzu diesels (the 1.7 and 3.0V6).

[ged.fi]

The only place they don't use additives in winter is Scandinavia, where the diesel is practically jet fuel anyway, and doesn't freeze until it gets down beolow -40°C.

Not true. All diesels have additives, the exact quantities and types depend on expected weather conditions. Additives also differ between chains.

In Finland, pumps are often marked "summer" or "winter" quality, but actually there are quite a few different types depending on geographic location, weather forecast, etc.

For "summer" diesel, you may have qualities such as -0/-10, -5/-15 and -15/-25. "Winter" diesel is -29/-34, and in some areas you get "arctic winter", which is -40/-44.

The chain I use has a winter diesel which typically meets -30/-39 even for the -29/-34 quality. This means that last time I filled up, they were still selling "-15/-25 summer" diesel.