Cold Start Violent shaking & misfire

[snapdragon]

Hi folks,
We just popped from Nottingham to Koekenhof, NL and back over the long weekend and the A8 ran as sweet as a nut and returned 47mpg on one 160 mile leg. The diesel in Belgium was only 80p / litre too.

We got home last night - but this morning, the car started normally and then misfired and shook quite badly with blue smoke coming out the exhausts. I turned it off after a bit and got my laptop with VCDS.
The only code was the usual engine mount solenoid and EGR insufficient flow but these come back frequently for a couple of years and have been no bother. I cleared them and restarted. It was still bad and after 10 seconds the smoke was cleared and vibration not as bad. After a few minutes the car was fine and I put it down to some oily soot dislodging in the intake.

Parked up all day and this afternoon, exactly the same, but took longer to clear, kept smoking and shaking and loss of power. Once up to about 80˚c it was perfect again.
When it has cooled off tonight I'll go out and check some more measuring blocks while it does it.

What the hell could this be? It is really alarming and clearly doing it no good. Could it be petrol in the diesel?
2006 3.0tdi

[PsYcHe]

Cheap Belgian deisel?

I'd maybe try an Italian tune up, seems to make the wife's X5 behave a lot better (and you get to pretend to be James Bond when all the crap comes out the exhaust like a smoke screen).

[M-A8]

Hi Snap
I can't imagine how you feel and I wish I was able to help in anyway, but that is out of my zone.
When I had a similar problem it was a simple misfire caused by faulty ignition coil which also was nicely pointed out to me by VCDS so it was and easy cheap and quick fix.

How about really a cheap diesel, or something mixed with, something what would stay at the bottom of the tank when cold and then get mixed slowly with the actual diesel when the diesel pump get to action properly and starts pumping more and more good stuff through??

I hope you will get to the bottom of it mate

[snapdragon]

Thanks chaps. It was a very nice petrol station. Automatic pay at pump only in a posh area called Donk. It was busy so would have had a high turnover and was only cheap due to the low tax and duty.

Last night I let it cool down to about 20˚c and it still did it a bit.
The idle was OK, but breathing on the throttle >900rpm reulted in a misfire which got worse the higher the rpm before smoothing out or not being noticeable at higher revs.

I measure the smooth running control in VCDS as injector 4 looks to be the odd one out and exceeds the upper limit of 2.99 mg/rev when the problem manifests.

I'll try again this morning. Put a bit more diesel and some 2-EHN additive in last night.

[centurion]

something that helped me in the past was Archoil AR6400-D... worth giving a go to clean up the system [as much as it could] and you could follow up with higher octane fuel afterwards to check if it is any better.

...at the same keep on monitoring in VCDS for any obvious issues/errors.

ps. i recently had MAF problems and it never came up in VCDS.

[snapdragon]

It has got worse and worse, so I unplugged injector no.4 wire and the smoking stops. Plug it back in and it starts again.
I have ordered a new injector and fitting parts and hope it's that rather than a dead cylinder with no compression or some such.
The injector was £230 from local motor factor and £30 for fitting parts from TPS.

[snapdragon]

Injector fitted - cost £250 with seals and plate but not really that much different but different nonetheless as it went back to being perfect when hot whereas before it started being bad when hot too.
Started to suspect I put petrol in when in Belgium but I am pretty sure it was the right nozzle. So I filled up with diesel and left to go cold and started up and it was 90% from cold. I now wonder if I put 60 litres of petrol in or they had a crossover at the station.
Dropped of at Audi dealership for more testing

[M-A8]

S**t Snap, so sorry to hear that. The last thing you want is to spend this sort of money and see little improvement.
Any update on the testing done by Audi??

(just please don't tell me it was the wrong fuel )

[snapdragon]

Thanks mate.
Audi wanted to replace a lot of parts rather than diagnose.
When I reviewed the footage of my camera, they just drove it from the carpark to workshop and then reversed back out to the carpark.
About 30 seconds. The LED display on the wall was telling them they were near their targets of finding £9k of work a day and a Fish & Chip treat was on it's way so they probably didn't want to get involved in a 10 year old car.

It is in the garage at work at the moment where some Automotive students will look at it.
Here are the fuel trims when the problem is bad. Once bank is lean to the limits of authority and the other rich. On a petrol car this would be asserted by feedback an O2 sensor on each exhaust manifold, not sure about a diesel as it only has one O2 sensor anyway. It is smooth running measuring blocks and I don't know how it is measuring this (with what sensors) or whether the fuel trims are a cause of the symptoms rather than an effect.

[snapdragon]

After replacing injector no. 4 and getting it to run but badly until hot. I next suspected no.1 so found that if I unplugged it before starting the car, it did not smoke or knock, it just had a misfire due to cylinder deactivation. When warm, I would pull over and plug it in and all was fine. About 6 journeys later, I forgot to unplug it and started the car and it was perfect and has been ever since. I now have an injector I don't need so will sell that after a couple of tanks of fuel. I don't know what the problem was but must have been water or something in the injector affecting it's operation.

NB- it is said that unplugging a piezo injector during the split-second it is open will leave it open and could damage the cylinder. It needs reverse polarity to close.

https://youtu.be/bfL-r2drdqA