Car cuts out after DPF removal

[matthewg]

Hey folks, looking for some help on an issue in my Superb 2010 1.9 TDi with 234,000 miles on the clock.

Last year I had the turbo replaced but ever since I had an intermittent issue where if I let the revs go too high in 3rd or 4th the coil light would flash and I would lose power, but switching it off and on again and it was gone. As I said it was intermittent and I became all too aware of when it might happen and would just change gear.

However it start happening in the mornings and I would also lose power on inclines too.

Reluctantly, the mechanic replaced the turbo again, and over the past month we have replaced the DPF sensor, the vacuum pump sensor, done 2 smoke tests, cleaned all the vacuum pipes, one injector was replaced and the rings on all the others were replaced, the glow plugs have also been changed as they showed an error, the boost pressure sensor was replaced, seals on the pipes were replaced,

The EGR has been mapped out too but the dpf is still there.
The head gasket was also done a couple of months ago.

The Error code it shows up is always P0299 but we have ruled out all the parts that are associated with the turbo, bar the engine itself.

Any help or insight would be greatly appreciated as I have 3 mechanics baffled as to what's wrong with the car and it's starting to really annoy me.

 

 

 

AS OF LAST WEEK

 

 

 

 

DPF clogged up finally last week  so I got it removed and mapped out.
It still felt like **** on the way home so went back the next day. Over the next two days we replaced the tandem pump and all injectors.
The car now cuts out, usually when I am slowing or stopping, and it takes 30-60 to restart.
The garage put my tandem pump back in and today I have replaced the fuel pump in the tank and guess what????

It still flipping cuts out. ARGH

 

Since the remap the cruise control no longer works

 

 

Has anyone ever heard of similar issues

[chimaera]

Cutting out points to fuel starvation issues.

 

The wiring harness to the injectors can fail on the PD engines. Part of it sits inside the head and the oil and heat rot the insulation away. Worth a look first.

 

Ross-Tech wiki on the P0299 fault code suggests looking at the vacuum system for leaks first.

 

I'd also find a competent tuner if you want to keep the EGR and DPF delete.

[matthewg]

Cheers for the reply Chimaera. 

 

I'll get the harness looked at tomorrow. 

 

We have looked at the Ross-tech Wiki and checked and changed everything they list 

 

The guys that done the tuning are supposed to be quite good at DPF & EGR removal. But I can get it checked out by someone else

[chimaera]

If you have access to VCDS, it might be useful to monitor and log MAP Requested vs MAP Actual while out for a drive. Try and force it into limp mode while you're at it.

[matthewg]

When I go back to the guys who remapped it, I'll ask them to do this. Although it hasn't gone into limp mode since the dpf was removed

[matthewg]

So I went back to the place that down the remap(who are also the folk that removed the EGR and remapped the car over a year ago) and the car is like brand new. 

They said they changed some sensors but basically the car was still in limp mode.

They didn't charge me for whatever they done but I suspect the remapping for the DPF had a glitch in it and when they remapped it again, everything cleared itself up(that's my guess)

 

Anyways, I have no idea what has solved the issue I had but it's sorted.YAY

[silver1011]

Good news!

 

I was on the understanding that blanking off the EGR on cars equipped with DPF's was a big no-no, as the lack of an operational EGR then puts increased load on the DPF, quickly killing it?

 

I didn't realise a DPF was fitted to the 1.9 engine on the Superb. Every day's a school day.

[matthewg]

Yes Silver, I was told this a few months AFTER getting the EGR blanked out and remapped. Didn’t kill it that quickly, or maybe it did and the car just didn’t cop that this was the issue. 

 

My car is the last of the 1.9 Tdi greenline from 2010.  

 

Next engines were the 1.6 or 2.0

[Breezy_Pete]

6 minutes ago, silver1011 said:

was on the understanding that blanking off the EGR on cars equipped with DPF's was a big no-no, as the lack of an operational EGR then puts increased load on the DPF, quickly killing it?

 

On what basis? Not the old  misunderstanding about EGR is 'having another go at burning stuff to clean up the exhaust'? That's not how it works at all.

EGR tends to increase, not decrease soot levels, but decrease NOx (it's primary purpose). Unfortunately, NOx helps to oxidise soot in the DPF so EGR flow increases rate of soot accumulation and decreases rate of its removal.

But changing anything in your emission reduction equipment is of course illegal, so...

[chimaera]

30 minutes ago, Wino said:

 

On what basis? Not the old  misunderstanding about EGR is 'having another go at burning stuff to clean up the exhaust'? That's not how it works at all.

EGR tends to increase, not decrease soot levels, but decrease NOx (it's primary purpose). Unfortunately, NOx helps to oxidise soot in the DPF so EGR flow increases rate of soot accumulation and decreases rate of its removal.

But changing anything in your emission reduction equipment is of course illegal, so...

It was common enough for EGR delete (possible still is) to happen alongside a performance remap, which could stray into a combustion regime that created more soot, thus shortening the life of a DPF.

 

One of the limiting factors for diesel combustion, and soot formation, is flame speed. For mineral diesel at CN 55, 5000 rpm is about the maximum engine speed that will allow complete combustion of diesel regardless of how rich or lean it runs. The synthetic diesel (~CN 72)used by Audi at LeMans allowed a rev limit of around 7000 rpm because it could light earlier and burn faster.

 

EGR's role is to reduce NOx formation by reducing or eliminating excess oxygen from the combustion process. Diesels are generally run lean which means there's spare oxygen available after the fuel has been burned up, and in a hot pressurised environment, elemental nitrogen can be persuaded to react with some of that oxygen and form NOx.

 

Recirculating some exhaust gas into the combustion chamber dilutes down the incoming charge and reduces the amount of oxygen present down towards stoichiometric but maintaining enough dispersion of oxygen to achieve better combustion than if the engine was running at stoichiometric and no EGR. Moving towards stoichiometric will increase the possibility of soot formation even under EGR conditions though, so it has to be judged carefully against the rate of NOx generation.

 

On DPF-equipped cars, passive regeneration occurs by using NOx in the exhaust to burn off the soot in the DPF if the exhaust is hot enough; it's highly likely that the EA189 emissions update is taking advantage of this, based on reports here plus correspondence I've had with Skoda and the VCA. The original SSP issued for the EA189 goes into some more detail on this.

 

The DPF-equipped PD engines had a lot of trouble because the DPF was added late in the engine's design life and never properly integrated into the system the way it was done on the CR engines. From what I've seen, most of the trouble was the distance from the engine to the DPF meant that the DPF cooled off too easily and couldn't regenerate as well.

[silver1011]

53 minutes ago, Wino said:

On what basis? Not the old  misunderstanding about EGR is 'having another go at burning stuff to clean up the exhaust'?

 

When my EGR failed I explored the option of EGR removal rather than replacement.

 

This option was quickly dismissed as all the reputable EGR blanking / bypass kit suppliers say that they're unsuitable for cars fitted with a DPF.

 

This is from Darkside's website...

 

Please Note: 

The EGR Valve should NOT be removed on vehicles that still have the DPF Filter in place, doing so may block the DPF as the EGR Valve operation is a prerequisite for DPF Regeneration.

 

https://www.darksidedevelopments.co.uk/egr-removal-delete/

 

Edited 16 October, 2018 by silver1011

[chimaera]

1 minute ago, silver1011 said:

 

When my EGR failed I explored the option of EGR removal rather than replacement.

 

This option was quickly dismissed as all the reputable EGR blanking / bypass kit suppliers say that they're unsuitable for cars fitted with a DPF.

I think that mostly comes down to the fact that most modern cars with EGR and DPF have those functions very tightly integrated into the engine's overall operating software and removing them cleanly without breaking other stuff is not trivial. Older engines like the PD had it added on later and AIUI it's easier to just remove the EGR or DPF code from those

[Breezy_Pete]

10 hours ago, chimaera said:

It was common enough for EGR delete (possible still is) to happen alongside a performance remap, which could stray into a combustion regime that created more soot, thus shortening the life of a DPF.

Makes sense.

 

Thanks for your detailed explanation but I knew roughly how it works already.

 

An awful lot of people seem not to though, and labour under the misunderstanding that EGR is about having another go at burning the exhaust material to clean it up.

It seems I was wrong to assume that silver1011 was one of these people, apologies.