octavia fuel problem

needthespace · 26-11-2011 4:04pm #1

i have a '09 octavia with 60,000km on clock, which up to recently was doing 60+ mpg.
lately it has started blowing black smoke at high speeds. i got it serviced and the fuel filter was clogged with thick gunge in the base. since then i have only been able to average 35 to 40 mpg.

any ideas greatly appreciated thanks.

Greyfoot · 26-11-2011 6:16pm

needthespace wrote: »

i have a '09 octavia with 60,000km on clock, which up to recently was doing 60+ mpg.
lately it has started blowing black smoke at high speeds. i got it serviced and the fuel filter was clogged with thick gunge in the base. since then i have only been able to average 35 to 40 mpg.

any ideas greatly appreciated thanks.

So the fuel filter change sorted the issue now? Black smoke on diesels are sign of rich mixture as a starting point. Someone with more knowledge will point you in the right direction.

Row · 26-11-2011 7:13pm

If it has a diesel particle (particulate) filter fitted then it may need to regenerate.
Do you do alot of short journeys...?

needthespace · 26-11-2011 9:42pm

Greyfoot wrote: »

So the fuel filter change sorted the issue now? Black smoke on diesels are sign of rich mixture as a starting point. Someone with more knowledge will point you in the right direction.

thanks for your reply Greyfoot,
im not sure the fuel filter has sorted the issue. im still getting only 35 - 40 mpg.

needthespace · 26-11-2011 9:47pm

Row wrote: »

If it has a diesel particle (particulate) filter fitted then it may need to regenerate.
Do you do alot of short journeys...?

hi Row,
i don't do a lot of short journeys but i do drive the car very easy and am seldom on the motorway maybe im doing more harm than good to the engine by driving easy??
what is regenerate and how do i do it?

regards
needthespace

Row · 26-11-2011 11:54pm

needthespace wrote: »

hi Row,
i don't do a lot of short journeys but i do drive the car very easy and am seldom on the motorway maybe im doing more harm than good to the engine by driving easy??
what is regenerate and how do i do it?

regards
needthespace

If your octavia has a dpf it will need to regenerate (clean) the diesel particulate filter every 4-500kms-ish depending on your driving..short journeys and not driving it on can cause problems with dpf's.

With any diesel its good to drive them on...drive as you do but once or twice a day bring the revs up to around 3000-3500rpms for a few seconds...this helps to clean out any carbon thats built up in the engine from low rpm driving.
The first thing to do is find out if you have a dpf...then if your car is still under warranty then let your dealer sort it...if not then get a good independent garage with the right diagnostic equipment to diagnose where the problem maybe....:)

Going by this the superb has a dpf...
http://www.skoda.co.uk/GBR/Documents/19246_Skoda_DPF_Leaflet_v7.pdf

Best of luck and keep us posted on your progress..;)

More info here..
http://briskoda.net/forums/topic/124041-who-has-a-diesel-particulate-filter-dpf/

CJhaughey · 27-11-2011 9:52am

Thick gunge in the filter? Check that the diesel hasn't been infected with a diesel bug. It's a bacteria that lives in diesel.
I would check/change the new fuel filter and see if it is clean.

needthespace · 27-11-2011 5:34pm

Row wrote: »

If your octavia has a dpf it will need to regenerate (clean) the diesel particulate filter every 4-500kms-ish depending on your driving..short journeys and not driving it on can cause problems with dpf's.

With any diesel its good to drive them on...drive as you do but once or twice a day bring the revs up to around 3000-3500rpms for a few seconds...this helps to clean out any carbon thats built up in the engine from low rpm driving.
The first thing to do is find out if you have a dpf...then if your car is still under warranty then let your dealer sort it...if not then get a good independent garage with the right diagnostic equipment to diagnose where the problem maybe....:)

Going by this the superb has a dpf...
http://www.skoda.co.uk/GBR/Documents/19246_Skoda_DPF_Leaflet_v7.pdf

Best of luck and keep us posted on your progress..;)

More info here..
http://briskoda.net/forums/topic/124041-who-has-a-diesel-particulate-filter-dpf/

thanks Row for your helpful advice.
the car is just out of warranty. the independant garage told me the fuel filter had never been changed even though the garage it was bought in had stamped the service booklet as having done so!

i'll let you know how i get on..

needthespace · 27-11-2011 6:43pm

according to the briskoda decoding instructions i do not have a dpf in my car so that's one less thing to worry about at least!

argosy2006 · 27-11-2011 7:04pm

Your air filter sounds like its blocked, New air filter, huge lack of air causes black smoke,

needthespace · 27-11-2011 7:24pm

thanks argosy 2006,
would a blocked air filter cause sudden high fuel consumption?

needthespace · 27-11-2011 7:26pm

CJhaughey wrote: »

Thick gunge in the filter? Check that the diesel hasn't been infected with a diesel bug. It's a bacteria that lives in diesel.
I would check/change the new fuel filter and see if it is clean.

thanks for your reply cjhaughey,
i'd hate to think that this would be my problem though!!

Row · 27-11-2011 8:41pm

If your engine has'nt got a dpf then black smoke is normally a sign off excess amounts of fuel been injected into the cylinders or as said above your airflow is restricted....e.g.blocked airfilter/airflow meter.....get a diagnostic check and see what faults(if any)show up...:)

needthespace · 29-11-2011 11:52pm

Row wrote: »

If your engine has'nt got a dpf then black smoke is normally a sign off excess amounts of fuel been injected into the cylinders or as said above your airflow is restricted....e.g.blocked airfilter/airflow meter.....get a diagnostic check and see what faults(if any)show up...:)

hi again Row,

im waiting on garage to fit air and pollen filter, and check the fuel filter again, so hopefully the problem will be sorted.
strangely though the fuel economy seems to be improving of its own accord and at the moment is up in the late 50s.
i'll keep you informed!

George Dalton · 30-11-2011 11:29am

Are you measuring the MPG yourself or going off the display in the dash?

needthespace · 30-11-2011 7:21pm

George Dalton wrote: »

Are you measuring the MPG yourself or going off the display in the dash?

I'm measuring it myself by filling to the neck and calculating. I don't trust the display.

George Dalton · 30-11-2011 7:46pm

Well if it has fixed itself then keep on driving

needthespace · 30-11-2011 11:37pm

George Dalton wrote: »

Well if it has fixed itself then keep on driving

i got fuel and air filter looked at by garage tonight, everything is perfect but the fuel consumption has fallen again, the mechanic was at a loss to explain.

George Dalton · 30-11-2011 11:40pm

Which engine is in it?

Slidey · 01-12-2011 12:07am

Are you loosing boost pressure by any chance. That may explain the black smoke

needthespace · 01-12-2011 12:07am

thanks for your reply george dalton. its a 1.9 tdi.

needthespace · 01-12-2011 12:12am

Slidey wrote: »

Are you loosing boost pressure by any chance. That may explain the black smoke

what does boost pressure mean? the black smoke seems to have corrected itself though.
im more concerned about the fuel consumption because i will be doing a lot of miles over next year.

Slidey · 01-12-2011 12:14am

If you were loosing turbo pressure from an intercooler pipe or intercooler you could have the symptoms you described. The clips where the pipes join can give trouble on these.

Have you noticed the sound of the turbo lately?

needthespace · 01-12-2011 12:30am

Slidey wrote: »

If you were loosing turbo pressure from an intercooler pipe or intercooler you could have the symptoms you described. The clips where the pipes join can give trouble on these.

Have you noticed the sound of the turbo lately?

no its a lovely quiet engine.

thanks for all the replies guys, i really appreciate them:)

needthespace · 03-12-2011 5:19pm

update: the fuel problem has seemingly fixed itself again and is currently doing 61.7 mpg. Hopefully this will continue.
The mechanic thinks it may have been contaminated diesel.

Thanks to you guys though throughout the last few days, I've learned quite a bit about the engine!!

Regards
Needthespace

chinwag · 03-12-2011 5:34pm

Interesting read. Must say I would have nearly sworn that a 2009 diesel engine would have had a DPF fitted but it seems from this thread that this is not so. Anyone know when DPF became compulsory in this country?

needthespace · 03-12-2011 10:49pm

chinwag wrote: »

Interesting read. Must say I would have nearly sworn that a 2009 diesel engine would have had a DPF fitted but it seems from this thread that this is not so. Anyone know when DPF became compulsory in this country?

I'm not sure if they are compulsory or not but I think the larger engines/cars have them eg. the superb.

I must say though I never expected the 1.9 to be so economical, my previous car was a 1.3 astra diesel with a supposed track record of 70+ mpg but I could never get more than mid to late 50s. Everything that could go wrong did and I almost had to give it away to get rid.

If you want to check if your octavia has a DPF check out post no 6 from Row on this thread and follow the link to Briskoda.

Dadda31 · 21-03-2012 7:14pm

That thick gunge is a sludge from the supplier tanks. Black Smoke is actually unburnt fuel so the conditions for combustion in your car isnt right and this is usually down to the fuel you put in.

if you want to improve your cars efficiency make sure the fuel quality is good and that there is no black smoke coming out of the car.

Chimaera · 22-03-2012 3:15pm

A diesel particulate filter is not of itself compulsory fitment to cars, but it's commonly fitted in order to meet emissions regulations specified by the EU. Fitmnent of DPFs has become common since around 07-08 as emissions standards have tightened.

As others have said, black smoke from a diesel engine means a rich mixture so either it's overfuelling or the induction system is underperforming. If the fuel filter is ok now, and there's nothing else wrong with the fuel injection system, it's time to point the finger at the air system.

First off, what year is the car? It's not enough to say it's a 1.9 TDI - there have been about 20-30 variants of the VAG 1.9 TDI made since it was introduced in 1993 and they're all different in their own way. Ideally, if you can post the engine code that'd be helpful too. It's a 3 letter code which will be on a sticker on the timing belt cover. It's also printed on the build label which should be on the inside cover of the service book.

Based on what's already been done to the car, my guess here is one of two things going wrong:

1. The vanes on the turbo are sooted up from the car being driven too gently - this can cause them to jam, intermittently or permanently. this can cause over or under boost. In your case, I'd suspect underboost - the engine is not getting enough air because the turbo can't open up enough.

2. Cracked or broken vacuum hoses, or faulty N75 solenoid - this will cause problems with boost control on the turbo and lead to not enough air getting to the engine.

You probably need to get the car to someone with VAG-specific diagnostics at this stage to see what faults, if any are stored. If they have VCDS, some additional on-the-road tests can be carried out to determine if there's a problem with the air system.

octavia fuel problem

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