"Depolution system inactive" warning on C5 1.6HDI

[Neil TM]

Hi,

I have just tried to bleed the fuel filter which it says to do with every oil change. I got a lot of gurgling and running water type sounds and less than a teaspoon of clear diesel out of it, and no water, so concluded, without much confidence that that job was done. Not sure when filter was last changed, and no tell tale date stamp in the plastic to give any clues. I didn't bother running it for 30 secs, just drove it, but it ran out of fuel while still reversing. Turning it over on starter wasn't getting me anywhere so I hand primed it, and it started OK this time, but put up the "Depolution system inactive" warning and now the engine management light is permanently on, with the same message repeated at start up. The car runs just as nastily as it did before I worked the filter, and is why I looked to the filter as a possible cause for flat spots and throttle response lags, and giving up while accelerating, which have always been present since I bought the car 13,000 miles ago, but appears to be getting worse. I've had no EM light come on until now.

The EOLYS was refilled and reset only 30,000 miles ago, so I don't see why a bit of air introduced at the fuel filter, and now purged should have done anything to that system. Never bothered the xantia 1.9td, but then this car appears to have come from an unknown planet.

Any thoughts would be appreciated on what has been causing the dismal running that others also seem to commonly report, and making the depolution system happy again? I don't have a lexia.

Thanks,

Neil T (56 plate C5 1.6HDi VTR)

[oneday]

hi neil have a look in the superstickys forum see if anyone is near you with a lexia

[BigBadBob]

Hi Neil
I have the 2006 (06) C5 1.6HDI Estate, but only had it for 3 weeks - so not really an expert. What you describe as flat spots and throttle response lags, I had assumed was normal for this engine with its (too complex for my liking) anti-pollution systems. It is annoying though. If you read my post on trying to avoid the well known turbo failure, you will see the EGR valve mentioned as a cause of black/sooty oil. What I have also seen described by various sources is that blanking off the EGR gives a cleaner pick up. As I drive mine, I rather imagine that those hesitations that occur are to do with the EGR valve opening/closing. I could be wrong and others may know better, but I am getting a blanking plate fitted on Tuesday, so can let you know once fitted. My only concern is that I may also need to get the ECU mapping modified, which I am still trying to get organised.

On the upside, I do think the 1.6HDI is remarkably good in terms of economy/power/longevity provided sensible maintenance is observed.

If you do find any other causes, please do update us.

[Neil TM]

Thanks for the replies guys. After a few more trips the 'fault' cleared itself and hasn't come back, so hopefully the car has changed its 'mind' about mugging me for my wallet!

The hesitant running is definitely worse than when I bought the car last March, so I'll probably throw £20 at it for a new fuel filter in the hope that it might be down to this.

When I bought the car it had just had a couple of new injectors because the old ones had worked loose in their threads which I was told is a breed fault on these 1.6 engines!!? I have no idea what sort of tool I need to check tightnesses though, as a socket won't clear the top, and there is insufficient access for an open ended spanner. Is there a special tool?

I can't think what else to check apart from air filter which looks OK. Besides which the hesitancies in running are most noticeable with the car in gear but under no load or overrun, but that is a new symptom. Mostly when cold, but at other times as well it will suddenly die in the middle of accelerating off in first gear, which having already waited for the interminable turbo lag is really not nice, or even safe IMO, and I've read others say the same thing. There's what you want and expect out of your right foot and what it decides to give you, with insufficient connection between the two.

I am aware that computer controlled fuel injection is not always executed well, but presume they must have got it right in some cars? We hired a brand new Zafira on holiday, the first to drive it, and it was unbelievably awful. Ridiculously high geared, and six of them as well. You'd struggle to get going and then suddenly the turbo kicked in and lurched you forward. Never driven a car easier to stall than that one. A hired new Nissan Micra also exhibited vague indecisive hesitant throttle response under acceleration as if it really couldn't make up its mind what it was going to do for you. But this C5 is the worst of the lot. There is no pleasure in driving it whatsoever, its just hideous.

Does anyone have one of these 1.6 HDi's that drives nicely and smoothly apart from what I presume is an inevitable turbolag because the smaller engine has insufficient power until the turbo kicks in? It is hard to believe after the perfection of the mechnically pumped 1.9TD Xantia that the new technology has made such a mess of things and that my car can't be faulty.

I will let the forum know if I make any improvement. Meanwhile I am on the lookout for a nice 1999 or earlier Audi A6 1.9TD, I've had it with 21st century cars. They seem to have abandoned the KISS principle big time introducing a myriad unnecessary faults to permanently undermine any confidence in the thing. Something that doesn't ration you to half an hour max listening to the radio without the engine running as well!



Cheers, Neil T (56plate C5 1.6HDi VTR estate)

[BigBadBob]

The EGR blanking plate was fitted today - and the throttle response lags and flat spots seem to have completely disappeared. It now drives with a completely smooth clean pickup, no indecision where it's not sure if it is speeding up or slowing down. In fact I would say it is now driving how I would expect a diesel to drive. It has become a pleasure to drive!!
So far, there have been no warning lights either, although I have done only about 25 miles.
What I wonder is if the car had these hesitations in throttle response from new or if they develop as the EGR becomes more caked in soot. Perhaps somebody with a lower mileage 1.6HDI can enlighten us.

[mooseshaver]

I've had this with a 1.6 and had new egrs, maf, fuel filter.

[Neil TM]

The EGR blanking plate was fitted today - and the throttle response lags and flat spots seem to have completely disappeared. It now drives with a completely smooth clean pickup, no indecision where it's not sure if it is speeding up or slowing down. In fact I would say it is now driving how I would expect a diesel to drive. It has become a pleasure to drive!!
So far, there have been no warning lights either, although I have done only about 25 miles.

Thanks for the update Bob, glad to hear your news. I had started to think it was probably the EGR valve as I could not match my hesitancies with the concept of fuel starvation, and frankly resent wasting any money on this car. As I understand it you should be free of any fault light for as long as the EGR valve carries on uselessly functioning and connected electrically obviously.

I wonder if it will pass the emissions test? Any further progress report, changes in fuel economy noticed - any further observations would be appreciated. I think I will probably follow you.

It would still be nice to know if anyone has one of these with the EGR valve in circuit who enjoys the nice lag free running. Anyone?

My only other encounter with one of these valves (on a corsa) involved a failure to decarbonise it to get it working again. Coprophagia is for rabbits. In humans and cars it is a perversion.

Thanks again, Neil TM

[Neil TM]

I've had this with a 1.6 and had new egrs, maf, fuel filter.

And?

Neil TM

[mooseshaver]

That was meant to be a longer reply.
The first egr seemed to make a difference. But two weeks later it was back. It never was resolved. It only happened when I drove the car and not anyone else and no faults in lexia.

[mooseshaver]

Actually sorry I've been posting in wrong place!

[Neil TM]

That was meant to be a longer reply.
The first egr seemed to make a difference. But two weeks later it was back. It never was resolved. It only happened when I drove the car and not anyone else and no faults in lexia.

Thanks mooseshaver, but most discouraging unfortunately. In the absence of anyone else coming to the defence of this car it is beginning to look as if they really are this awful by design. Perhaps it takes a while for a new driver of the car to fully notice our experience.

After Bob's encouraging post I decided to blank off the EGR valve as even the objectively neutral wikipedia entry on EGR valves in relation to diesels could find nothing positive to say about them at all - all negatives. It even states that they cause extra particulates which is why they are then followed up with the filtering and EOLYS combustion of the soot. it really is a road diesels should never have been forced down, correcting one fiasco with another, but not quite managing it while annihilating the supposed 15% fuel efficiency improvement over indirect injection.

If doing this job, it is necessary to remove the bracket that holds the fuel filter (3X bolts) as it is impossible to slide in the blanking plate with it in place. The offending object is at the back of the engine on the nearside, and not easy to see. The Haynes manual has a picture. One of the two EGR retaining bolts is visible, the other completely hidden by pipework and lower down, but reachable by feel eventually! Mine was completely loose when I came to it! This is a car no other amateur has ever touched btw!

I've done getting on for a couple of hundred miles since then and can report, like Bob an immediate improvement, in fact I thought it was cured, but then started to notice there were still vaguenesses and lacklustre acceleration. It still pulls back sometimes on accelerating away in first gear (no other gear), going completely flat, whereas when it did it before it simply died, preciptating an emergency gear change into second just to rescue some momentum. So it has improved from dangerous to dismal.

Although the abandonment of acceleration in first gear happens most when cold I also noticed it around town after an 80 mile motorway run, yet, just as before it doesn't always do it. I really cannot work out what's going on, so the hunt is still on for a nice Audi A6 since this seems to be an unresolvable mystery.

How could they follow the seamless Xantia 1.9TD with this?! http://www.frenchcarforum.co.uk/forum/p ... b1f9c0f9ea#" onclick="window.open(this.href);return false;

Neil TM