Audi A4 2.0 TDI Rough idle

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Re: Audi A4 2.0 TDI Rough idle

Postby nelnun » Mon Feb 26, 2018 11:29 am

Shooter wrote:Can we see a Crank Sensor waveform, with at least 4 or 5 revolutions across one screen, when it is running bad ?

Hi shooter, thanks for your reply! I don't have it, it is really hard to access the sensor! But why would that be a problem if when I simulate a coolant temp below 40ºC or above 50ºC it idles perfectly? :roll:
Thanks
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Re: Audi A4 2.0 TDI Rough idle

Postby nelnun » Tue Feb 27, 2018 12:22 pm

On the 1st and 2nd red box, coolant temp was set to ~33ºC and it was idling perfecly, as you can see on the RPM flat line.
Then, the 3rd red box, I've increased coolant temp to 120ºC (fans stared spinning, message in the MFD and red temp light on) and it was idling perfect as well, but the reason here was probably due to the opened EGR.
In this coolant emulation temp test, even above 50ºC, it still failing, but rough idle will happened always when I start engine with a coolant temp between 40-50ºC, according to all of my tests! What an odd thing!
Software issue? I'm tempted to do the dieselgate fix to check if the problem goes away, but I don't want the fix... perhaps, it be mandatory next year...
Coolant_Emulated.jpg
CoolantTemp
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Re: Audi A4 2.0 TDI Rough idle

Postby Shooter » Fri Mar 02, 2018 3:04 pm

Hi shooter, thanks for your reply! I don't have it, it is really hard to access the sensor!


I agree that it is not easy to access the CKP on this engine but "No Pain - No Gain" You should be able to get a reading somewhere in the loom or at the ECU itself

But why would that be a problem if when I simulate a coolant temp below 40ºC or above 50ºC it idles perfectly? :roll:
Thanks


What I am experiencing with these VAG CR Diesels of this era is that they do suffer from Injector faults with various symptoms. For example:
1. Misfire, shuddering only for a few seconds, only when cold.
2. Fuel pressure loss at heavy load only
3. Straightforward, constant misfire
4. Incomplete combustion smell
.... .......... ................

The odd thing is that it always (in my cases) just one injector, more surprising is that it always Injector 2 or 3 and none of these vehicles ever come back with another injector failed. It is as though some one is fitting one sub standard injector to each engine ??? :shock:

I note that you can manipulate Coolant Temp and promote change in that engine. The reason behind asking for the CKP signal is to establish what contribution each cylinder is contributing to engine rotation.

Also the fact that you have had this issue since you purchased the vehicle, in my head, raises alarm bells about software / bad mapping. My advice is that you get the "NOx Fix" Update done at the dealer. As part of the update you will get an additional 2 year warranty on all related parts ie. EGR, Injectors ..... ..... ...... ......

This could be your trump card
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Re: Audi A4 2.0 TDI Rough idle

Postby nelnun » Sat Mar 03, 2018 4:53 pm

At the moment, I can discard the injectors, once they were already replaced (refurbish by bosch)! Reading the injection deviation oh the 4 injectors, when it is failing with rough idle, there are always one cylinder that increases deviation above 1mg/str, but it a kind of random thing, as sometimes is #1, other times #3, #2, 4#.... It seems to be trying the warm up phase (injection quantity increases quite a lot, from 5mg/str to 8/9/10, always oscillating around these values) for a regeneration before coolant temp reaches 80/90ºC?!

My problem is if I do the FixUpdate and the problem still persists, I'm back to "ground 0", but, I have to give it a try...
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