Audi A8 4.2 TDI - gearbox judder

[c3nturi0n]

hi guys,

and i'm new to this Audi /VW forum [having spent some time on other Audi related ones in the past].

i recently bought an A8 L and it's been a magnificent car for months only to notice slight judder/shudder [e.g. hesitance] recently. it is mainly manifested when eng temp is still relatively low in 2nd and 3rd gear when moving slowly through gears @ 12-1600 rpm. If one was to push the accelerator pedal hardly you won't notice anything.

i read several articles about g'box oil change but before i go down that route could anyone shed any lights what could be an issue... car had 140k miles on the clock and it has been maintained regardless of cost by the Audi main dealer.

i also have access to VCDS and have attached extract re only transmission related error...


Address 01: Engine Labels: Redir Fail!
Part No SW: 4E1 910 409 A HW: 4E1 907 409
Component: 4.2L V8TDI A000AGMª0070
Revision: --H01--- Serial number: AUX3Z0F0383728
Coding: 0011773
Shop #: WSC 00097 210 80549
VCID: 224B0C03FD3A2A0EA27-8077


1 Fault Found:
006217 - Please check DTC Memory of Transmission Controller
P1849 - 008 - - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 227660 km
Time Indication: 0
Date: 2015.02.05
Time: 00:00:07


Freeze Frame:
RPM: 0 /min
Torque: 3.9 Nm
Speed: 0.0 km/h
(no units): 0.0
Voltage: 6.54 V
Torque: 795.6 Nm
Bin. Bits: 11000000


Readiness: 0 0 0 0 0


-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 09E-927-156.lbl
Part No SW: 4E1 910 156 P HW: 09E 927 156 B
Component: AG6 09E 4,2lTDI RdW 0030
Revision: --H01--- Serial number: 0076614
Coding: 0000001
Shop #: WSC 02313 785 00200
VCID: 306FF64BA3D6889E243-8065


No fault code found.

[EG-4.0TDI]

Hi,

Are you sure this is gearbox related rather than engine related? Cold low rev hesitancy in gear might be related to glow plugs kicking in and out, fuel injectors or possibly even one of the two MAFs acting up?
Just a thought and I might well be hopelessly wrong but if it was gearbox, I would have expected some other symptoms such as: hesitant taking off from standstill, harsh changes (up and/or down the box), flared up-changes, chirping noises changing up between 3rd and 4th under power - have you got any of those as well?

Can you reproduce the symptoms you describe when manually holding it in 1st or 4th (ie if symptoms manifest between the same rev ranges in all 4 gears when the engine is cold it would point more to engine than gearbox - although admittedly not conclusively!).

[c3nturi0n]

Hi.. Now you got me confused :(.

Yes it can be reproduced in tiptronic mode either using gearbox option (+ or -) or via paddle shifts.

I tried the same in N or P when parked... All fine.

Just to add i did several vcds scans over last no. Of days and none would point to Maf or engine as indicated above as no errors were shown. It does not however mean all is well but that would be my confirmation. Any other hints/suggestions?


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[c3nturi0n]

quick update...

successfully cleared all faults however that hesitation/juddering is still present.

I will try and eliminate the combination of MAF + EGR over next couple of days by disconnecting the earlier and [manually] cleaning the latter [will be a weekend job i'm afraid]. i also plan to complete gearbox oil change regardless so all in all i hope that one of or combination of all listed options will provide the cure http://forum.a8parts.co.uk/images/smilies/smile.gif.

One other options in the 'quick win' book though... i ordered Archoil AR6400-D Pro PEA Concentrate Diesel Cleaner that does apparently help with removal of gunk/carbon in EGR and vacuum pipes/lines so hope that should give meat least an indication if MAF/EGR is indeed the culprit in this case or perhaps something else.

Fishing continues http://forum.a8parts.co.uk/images/smilies/thumbsupsmiley.gif...

[vwpassat]

try revving the engine in park very slowly and maybe hold it at 3000 revs or the revs it would typically judder. If you notice a vibration then could be something unrelated to the gearbox like injector, maf, Air intake,etc

edit.. you must have tried that from the above posts :Blush2:

[c3nturi0n]

Yup did that already... I did put in AR6400 and have only driven for a shortwhile and it is considerably less so.

As you pointed out it seems that the issue is somewhere MAF - EGR related.

Q: can i pull any readings from Vcds re EGR and or MAF for clues?

Wanna get dirty this weekend but with two little boys that's almost impossible :)...


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[c3nturi0n]

Hi guys any suggestions?


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[EG-4.0TDI]

Not sure about the EGR but for the MAFs you could try just disconnecting them. Doing so will definitely cause error codes that will then need clearing, but the engine should revert to running on a default map without relying on the MAF load inputs.

Therefore, if you disconnect both MAFs and the engine runs better then you know the culprit is one of them. At which point, you can re-connect one of them and see if it is still OK - in which case the disconnected one is the troublesome one.

From recollection, you can disconnect them at the harness in the bottom of each of the air boxes (you will need to open them up and remove the air filter element to gain access).

[c3nturi0n]

i was suspecting that could have been the case.

I unplugged MAF's in turn and car started to run okay... I had them unplugged for over a week to monitor the situation and the issue I reported went away [albeit Check Engine was on which was least of my worries while in troubleshooting mode].

Thinking [will elaborate later on why?] that was the culprit or my probs I ordered two replacement Denso parts [110ish in total] vs. Audi's OEM that are manufactured by Denso at the cost of 160 each. I took the car to my mechanic who had been maintaining all my vehicles for last 10 years - fitted parts - and the issue returned. SO it seems that MAF is not the problem?!

in the meantime I took the car for 2500 mile journey around Europe recently and it had been fine throughout the journey... the only think I notice now is that misfire/shudder/judder @ 12-1500rpm is bit more evasive while the engine is warming up during the drive. once optimal temp. is reached it runs smoothly. again I disconnected MAF's and it had been fine ever since but guess what's bothering me is what's the d**n issue??

to add... I re-run VCDS scan several times to no availa and there were no obvious signs/errors flagged in the tool.

Any suggestions or hints?

[EG-4.0TDI]

Seems there are three possible options:

(a) One of the new Denso units is faulty - relatively small possibility but not by any means unheard of
(b) Both of the new Denso units are dodgy (very unlikely but theoretically possible)
(b) there is something upstream of the MAFs that is only used when they are plugged in that is causing the issue.

If it were me, I think I would seek to rule out (a) first. If you have two old Audi Units (A1 and A2) and two new Denso units (D1 and D2), I would try the permutations to try and find the dead ones.

Hypothetically, we have 1 malfunctioning Audi unit and 1 malfunctioning Denso unit and we know that:

A1 + A2 = trouble
D1 + D2 = trouble

So try:

A1 + D1 = ? If trouble then:
A1 + D2 = ? If still trouble then:
A2 + D1 = ? if still trouble then:
A2 + D2 =? if still trouble then either (a) both of the Denso units re faulty or (b) it's not the MAFs and we need to start asking questions about components that the MAFs feed into when they're plugged in and active.

Final thought - are you running standard air filters (and are they in good condition)?

[c3nturi0n]

Thanks for your feedback... That's something i thought off to and will give it a go next weekend.

Car has got full Audi sh and it was last serviced 10 months ago having done 5k since then... Filters are as new.

I suspect it is something to do with vacuum/air run when cold-ish which isn't providing sufficient feed (reading) to ecu causing it to misfire...


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[blodnob]

Hello there.
Did this problem ever get resolved ?
Seems I have the exact same problem.

[c3nturi0n]

Yes... I sold the car :).

2 injectors were off with additional 4 on its way out.


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