I drive a five year old SDI estate. The engine is absurdly under powered and it's only redeeming feature has been excellent fuel economy. Over the last few months this has been getting steadily worse. The car's done 60,000 miles, has always been dealer serviced and has just had the cambelt changed.

I took it to the dealer who ran a diagnostic on it and said he couldn't find anything wrong. The best they could suggest was that I dropped it into second gear and reved it up to the red line to clear out any sooty deposits. They also suggested trying a fuel additive to clean the injectors. I've done both these things (well not quite to the redline) and nothing has come out of the back end and the economy is still poor.

I do mostly motorway driving and used to get between 65 - 70 mpg, now it's between 50 - 60.

Any ideas what I should do next?

Any dealers/garages in herts/cambs area anyone can recommend for this sort of thing?

I've been told this engine is good for at least 200,000 miles and I have hardly hammered it so I can't accept that this is the result of wear and tear.

Thanks

Are the smoke emissions worse than before? If the car is overfuelling then this would be evident. Overfuelling on a diesel would be caused purely by the car thinking there's more air coming in than there actually is. This would be the MAF I would think.

Take it for a good thrash. RED LINE it, it won't do any harm, just make sure its up to temperature before you do.

Has it been regularly serviced? The other thing is economy always drops in the winter months.

EDIT: just read its been dealer serviced... Maybe the cambelt was put on 1 tooth out knocking the timing out slightly? Clutching at straws here!

Thanks for the responses.

I thought the cambelt change may be linked to the drop in economy but I wasn't mechanically minded enough to argue the toss with the dealer.

As for it being overfuelled , there seems to be little or no smoke coming out of the back end except when I start it up and then it's still very little.

forgive my ignorance but what is MAF???

What state is your air filter in and does the car smoke a lot under power?

Chris

No real smoke emissions under power

Air filter was changed at 40,000 mile serivice in December 05. I've no idea where it is to check it or what state itr should be in.

i should mention that the engine also seems to 'bang' a lot more than usual. It's always been noisy but now even when it's warmed up it makes more of a racket than it used to. It gives the impression of working a lot harder than it needs to.

That seems quite a long time for an air filter. It's a cheap part so might be an idea to change it and see. Not seen an SDI engine to give specifics on where it is... I would look for roughly square box with a clip off lid and a plastic tube / hose running to it on right hand side of the engine bay. Sure someone here can confirm or correct this.

Steadily worse - are you sure it isn't only over the last few months ?

Winter diesel - less calorific value than normal.

Beginning mid-December there were lots of Forum members complaining their fuel consumption had dropped quite markedly.

Plus, with the colder, wetter weather you're going to be using ancilliaries more - heater, heated rear window.

I'd also very much second what other Forum members have said about the air filter (Skoda reckon on 40k changes, mine had 16k and was grey all through so I changed it. 40k is way way too optimistic).

Possibly, try (as many other Forum members use) Millers Diesel Power Plus or the newer Sport 4 diesel additive. Around

I had the cambelt replaced on my old SDI and the 3rd party dealer put the belt on wrong. More of a clatter from the engine, sort of tractor like. Fuel economy down and lost power. If the drop in economy and noise coincided with the belt change. Then take it back .

I had the cambelt replaced on my old SDI and the 3rd party dealer put the belt on wrong. More of a clatter from the engine, sort of tractor like. Fuel economy down and lost power. If the drop in economy and noise coincided with the belt change. Then take it back .

I'd agree with this but I'd have expected it to throw a code in this case if the belt was on wrong & I'd also expect you would notice an immediate degradation in consumption/performance. :confused:

Anyway, I'd say it'd definitely be worth getting the valve timing checked again (maybe at a different garage) as it could well be causing the symptoms you describe.

Many thanks for all the responses.

I'll have a go at changing the air filter myself (presumably you can buy it from a halfords????)

As for the cambelt, I can't say I noticed a dramatic decline in economy (though I wasn't really monitoring it tht closely before the belt was changed). It does seem noisier though and there seems to be less torque since the cambelt was changed.

The air filter I would change every 10k miles having seen what came out at the recommended 40k interval. I lost 10MPG on the back of a filthy air filter. It's only £10 from the dealer and IIRC halfords were in fact more last I looked.

Also if it is banging more is the timing right? Just wondering whether the timing is out by maybe 1 tooth, such that the engine will still run, but not smoothly.

If the problems started when the belt was done I'd definitely check this, however i don't know if this is possible on this engine.

My sdi is a little poor at the moment as well im only getting fifty something , thats with 150 miles /week motorway 150/week commuting I also find that nursing it on the motorway dosnt help it too much it would rarther sit at 70-75.

Having said that i dont find it underpowered at all!! and thats after driving a tdci at work , it pulls like a traction engine and other drivers have even called it nippy!!

maybe i will downgrade to a vrs one day:)

Don't know if anyone is still reading this thread but thanks to anton for that last post. That almost exaclty mirrors my own experience.

since i posed the question I have changed the airfilter, fed the damn thing various additives (including millers diesel power plus thingy) AND taken it to another dealer who gave it a clean bill of health.

But still the mpg is down. The last dealer suggested it might be due to some tiny upset in settings when the cambelt was changed (couldn't follow exactly what) but said this was unlikely and would involve stripping the engine to check.

It still only manages late 50s/early 60 mpg even on long steady slow runs when the air temp is not too bad. It used easily manage around 70 on that sort of run.

AND it still seems to bang a lot more than it did pre-cambelt change.

As per the last post, it also seems a lot happier at higher speeds on the motorway and driving it gently seems to actually have a detrimental effect.

I've run out of ideas of what to do next and I'm just living with it hoping the warmer weather will impropve things.

After 2 years with this car, I have to say I agree with what has been said elsewhere here ie that this is an engine that really has no place on the road these days. It is SO underpowered, economy is it's only redeeming feature and when that begins to slide.....

I can defend the SDI I think it is a great engine for a number of reasons. if you forget the 0-60 time. it has so much going for it. very economical, round town it is as nippy as my octi vrs, put it on the motorway and wind it up it goes all day up and down hills, it is a fantastic for pulling a small boat round. when I am driving it you just have to remember that it is a different driving method. I would still rather have the SDI over the old 1.4 any day as it is more economical not much slower 0-60 and will definitely keep going up hills 70mph.

if all this coincided with your cambelt change go back, when the belt is changed the fuel pump timing is set at the same time if the seventeen year old main dealer mechanic couldnt be bothered to lock the pump hey presto timing out and no fault codes will show.

It gives the impression of working a lot harder than it needs to.

The slipping clutch on my vRS was quite unobtrusive, but was quietly robbing me of 6 - 8 mpg because the engine was revving harder than the roadspeed would suggest.