2.0 TDI Rough Idle (judder), and Excessive Smoking from Cold Start

[Lion Heart]

Hi guys

Hoping you can help me out a bit with this as done a lot of research online and found LOTS of people having the exact same/very similar issues with their 2.0 TDI engines across the Audi range. Mine is the A6 2.0 TDI 2008. However, in all the research I did nobody was providing a single solution. So hoping someone may recognise my symtoms...

When all warmed up seems very happy indeed.

However, from a cold start the revs can be a little juddery. You can feel a light shaking to the car. When you increase the revs it seems to 'stutter'.

I have taken a video. You may be able to make out the light shaking/juddering. Watch as revs increase:



This is accompanied by excessive smoke, which I would say is white. Check it out:



Any ideas very welcome!

 

[Lion Heart]

Quick update on this...

Today I removed the EGR valve. Yes, dirty and some carbonin there, but nothing ridiculous. All cleaned and ready to refit.

I also connected up Vag Com which showed no issues on the auto scan. I did the live data and tested 013 injector quality quickly.

Admittedly engine was not particularly hot (especially at first).

I noted on idle injector readings fluctuated a bit, but at one stage I saw this:

-1.01 -0.05 1.22 -0.28

I'm not an expert at all on these readings, but I think from my research that up to =-1.1 in acceptable?

So injector 3 a little high there. But like I say, it fluctuated and dropped back down to normal levels, and all four seemed reasonably happy.

So then I revved up to 2,000 ropm which is where the stuttery/judder happens as per my video above. I got this readon this time, which I could repeat with similar results each time:

2.31 All others around 0.78 mark

So injector 1 standing out on it's own with a high figure running up to 2,000 rpm. I assume that can't be normal?

 

[Lion Heart]

A friend pointed out that ifit were an injector, wouldn't it play up all the time, not only when the engine was cold?

 

[chefnikosdaniil]

The smoke could be the head gasket or for all of your symptoms also can be low pressure fuel pump vacuum pump(tandem)
You need to check if you have oil in your tank somehow or then you change fuel filter see if the fuel in filter is black, if so it’s definitely the tandem pump.


Sent from my iPhone using Tapatalk

 

[chefnikosdaniil]

If you run with faulty tandem for long time that can cause a problem to your injectors(clog them as you have a lot of oil in your fuel) maybe that’s why your readings are like this.


Sent from my iPhone using Tapatalk

 

[Lion Heart]

Thank you for that. Quick uestion, if it were the head gasket it would snoke permanently though, not just when cold?

Same with the tandem pump?

Or would either of these only play up when the engine is cold?

 

[marsmail]

Not sure if this is relavent or not, but recently had all 6 injectors on my 3.0 Tdi changed. I was told by the workshop that the max "delay" was 10 milliseconds (no idea what that really means) and on test one of mine was OK all the others were well over. I beliecve it has something to do with not shutting quickly enough and allowing fuel to dribble into the cylinder when it shouldn't - it can (I am told by the workshop) cause dilution of the lubricating oil due to the excess fuel finding its way to the sump.
I was getting whitish oil smoke on cold start which was OK when the engine warmed up although there was no shuddering noticeable.
After the replacement, the smoking is gone and the engine is noticably more responsive and fuel economy has improved a bit too.

Like I said, dn't know of this is relavent, but personally I would get it checked by someone who knows.

marsmail

 

[Lion Heart]

Thanks for the input. Wow, 6 new injectors must have cost a pretty penny!!! :-(

Yes, mine definitely has bad shuddering. I'm thinking possible vacuum leak as the next thing to test for.

I tested the EGR valve using VCDS and that seems to be working fine. I'm going to remove and clean the inlet manifold and put a new gasket in there whilst the EGR is off as well.

Then test for vacuum leaks.

If I still get no joy I'll then look in more detail at the readings for the injectors and run some tests on the engine when warm.

A case of elimination

 

[owais2k1]

If you run with faulty tandem for long time that can cause a problem to your injectors(clog them as you have a lot of oil in your fuel) maybe that’s why your readings are like this.


Sent from my iPhone using Tapatalk

I had this on my A6. No smoke though.

The engine was rough near idle and jerking.

Tandem pump changed and the problem is sorting it self out.

I had the tandem pump changed they also cleaned out the fuel tank.

Best way to check, is to remove the oil filter and cut it open. mine was black from oil contamination.

Hope this helps.

 

[Lion Heart]

Thanks guys!

Well, inlet manifold also removed and cleaned, again pretty tidy already.

Ran a quick check for vacuum leaks and could not find any.

I ran some injectors cleaner through the fuel and took readings from the injectors when engine warm a few days later, and getting decent readings back on those.

I also did a full service on her as well, including coolant change.

HOWEVER, the smoke has now virtually stopped!!! I'm wondering she had too much oil?

There is still the juddering when cold, but not half of what it was. And no smoke worthy of a mention!!!

So that's good news!

When I did the service I also change the fuel filter. I poured out the old fuel, and it was bluey. But remembered that the additive to clean the injectors was green, so mixing that with yellow diesel would equal blue. No oil in it as such (i.e. nothing trying to float or sink), but the whole lot dark blue in colour, but think that's likely the injector cleaner.

NEXT: I have spotted that the cambelt (which was a DIY change by the previous owner) tensioner is not set correctly. It has an arrow which should sit within a groove (slot) on the rear plate, or up to 5mm to the RIGHT of it. Mines 5-10mm to the left of it!!!

So looks like I'm going to have to remove and refit a new cambelt as well and make sure that the timing is 100% spot-on.

Found a LOT of reports on the forums (mostly from 2.0 TDI owners) experiencing rough idling and smoke after a cambelt change. So getting that cambelt 100% spot-on won't be abad thing!!