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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Re: Audi A4 2.0 TDI Rough idle

Postby nelnun » Wed Jul 25, 2018 9:55 am

Hi all!
Just a quick update!
I've bought ODIS to upgrade/downgrade the ECU software.
I changed it from version 6190 to 5597 and nothing has changed! Then, I changed it from 5597 to 9980 (fix file) and the rough idle problem has just disappeared!
Maybe, the issue is still there, but as the injection process is now different, the issue doesn't came up, who knows...

Anyway, I would prefer the sporadic rough idle then the fix file, but I will test it for a while!
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Re: Audi A4 2.0 TDI Rough idle

Postby nelnun » Wed Aug 22, 2018 5:03 pm

Hi all,

I've been doing a lot of logs to try to understand what is going on!

After rollback to v.6190, the problem came back!
I've made some tests to the PRV and IMV with a PWM emulator, as following:
- PWM emulator on the IMV: PRV is able to maintain rail pressure stable from 0% dutycicle until IMV fuel "cut off", around around 80%(?).
- PWM emulator on the PRV: IMV is able to maintain rail pressure stable in a very short dutycicle interval, when compared to PRV, between around 15% and 20%. Below 15%, pressure starts to drop, above 20% pressure "jumps" to 320bar.

I would say that this is expected, IMV is a "gross pressure regulator" and PRV is a "fine pressure regulator"!

During this tests, at idle, I was able to see the ºBTDC started at -0.6 (coolant 23,3ºC), then -0.9 (coolant 27,0ºC), -1.2 (coolant 34.2ºC) and when it reaches 39.6ºC, the BTDC jumps from -1.2 to -2.5 with no apparently reason and is when the rough idle starts and #1 Injection Deviations starts to increase above 1mg/str (the max loged is 2.8mg) and now (after 4 x injectors replacement) it only happens on cylinder 1!
The funny thing is when I "kick" the accelerator pedal all the way down, even just for a fraction of a second, the idle is back to normal!
This does not happen with the Fix Nox software (9980)! I think that it only fails when the injection map switchs to "low emissions map", because the injection timing goes from -1.2 to -2.5 and I've found out that one way to reduce Nox is increasing the injection timing! When I kick down the accelerator pedal, I think, it switchs back to the normal injection map!

Must be there an hardware issue anyway, as this does not happen in all the engines like mine!

I've found in VW erWin a TPI from 02/09/2010 (2023897/1), talking about a know issue about roller rocker arm incorrectly mounted at factory the would cause erratic idle and could make some noise from engine head below 2000rpm, no fault codes showed!

chnical product information
Transaction No.: 2023897/1

Engine: erratic idle speed, rattling noises from engine
Release date: 18-Aug-2010

Customer statement / workshop findings
• The engine runs erratically at idle speed and up to 2000 rpm. There may also be noises in the cylinder head area.
No entry is logged in the engine control unit.

Technical background
• The roller valve lever is not in the correct position. As a result it can jam or jump out.

Production change
• Optimised production

Measure
• Check the idle speed rest control of cylinder 1-4 via the guided functions. With deviations of +2mg/h per cylinder, remove the cylinder head cover. Check whether the roller valve levers of the affected cylinder are in the correct position.
• With fallen-out or broken levers check the complete valve drive for consequential damage.

...


Could this roller issue be checked/confirmed with a compression test? Without removing the head cover?

Thanks and sorry for the long post :)
Last edited by nelnun on Thu Aug 23, 2018 10:15 am, edited 1 time in total.
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Re: Audi A4 2.0 TDI Rough idle

Postby RYM6746 » Wed Aug 22, 2018 7:54 pm

With the WPS 500 you can definitely check valve opening time in relation to crankshaft degrees. You can compare this to every other cylinder if you dont have a spec to go buy. This will tell you if any of the components that operate the valve are worn/defective
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