BMK 3.0 TDi hunting erratic idle revs ( Have I got the most lemon A6!!! )

[gupsterg]

Hi Jim,

Sorry 4 very late reply, been really snowed with stuff. Yes family well and YES normal owner would be chuffed with my car but I'm not normal! LOL , ******* OCD to the Max mate, anyway car has been behaving and only very rarely have bout of rev hit miss, hoping once intake/EGR fully decoked all be well otherwise as soon as budget allow I think I'm go a trade her in for a nice pre-reg Skoda Superb estate, preferably LK edition.

ATB
G

[MarkTM]

a nice pre-reg Skoda Superb estate, preferably LK edition.
G

Good choice which engine/tranny combo? 140/170, manual/dsg, FWD/4x4

A LOT of car for the money!

[gupsterg]

As always thanks for your support Mark , as to which Superb I think we'll discuss in another thread/PM mate.

ATB
G

[man le-mans]

Nice to hear you can now look the other way ( turn a blind eye ) to the cars problems but sometimes it's the only way. Or as you say get shot of it as there are more important things in life than a car. I sort of understand how things can get to you mate as I'm a little ODC at times and what can seem small or nothing to some one else can grate the hell out of me.
Good luck

[Danodrisk]

My car is a 2005 55 plate 80k on clock... I am getting theses erratic idle revs on start up... I am suspecting my throttle valve body maybe issue... below is VCDS log...

-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Part No SW: 4F0 910 401 L HW: 4F0 907 401 A
Component: 3.0L V6TDI G000AG 0040
Revision: --H01--- Serial number:
Coding: 0011772
Shop #: WSC 02334 785 00200
VCID: 254BDA7FECF6CC30723

1 Fault Found:
17953 - Throttle Valve Controller
P1545 - 002 - Malfunction - Intermittent
Freeze Frame:
RPM: 1134 /min
Torque: 7.8 Nm
Speed: 40.3 km/h
Voltage: 13.91 V
Duty Cycle: 93.9 %
Bin. Bits: 001
Mass Air / Rev.: 499.4 mg/str
Voltage: 0.000 V

Readiness: 0 0 0 0 0

-------------------------------------------------------------------------------

Ross Tech explanation Link:- 17953/P1545/005445 - Ross-Tech Wiki
I've cleared this fault and it has not come back yet.... I have no other faults codes occurring ...

I have checked measuring block 18 on [01] Engine module in VCDS... again reactions seem correct on throttle...



When I was googling around for my issue I found this thread Link:- Audi A6 3.0 tdi hunting revs I have also posted here as well Link:- C6 A6 Lemans 3.0tdi fault.

So another is having issue like mine but no one yet advise on fix... my first year with car been turbulent I really thought I was picking up a cracking car... now spent £4k on it in first year... and this issue makes me feel

Maybe if I go get that remap I've been thinking about this will happen Link:- Dyno Tuning Disasters Compilation! 30 Horrific Dyno fails explosions and accidents - YouTube
Then I can move on...

Thanks in advance for any insight...... from anyone.... I need forum support

Hi, hope ur car is ok now, I have just bought a 3.0tdi quattro 2005 a6 only 4 months ago from UK and im over in germany now for a while. I have exactly the same symptoms you had, it seems ok in morning wen cold but as it gets warm the Rev pin is bobbing a bit and car shaking, and wen im just about to stop at traffic lights it sometimes has a medium-harsh engine tremble, its pretty scary :/ not really any power issues though, and it doesnt smoke wen driving but if i leave my car parked running at idle for 10-15 minutes it starts to smoke quote a lot??? Now, the language barrier with the german mechanics is hard enough and up to now in the 2 months ive been trying to sort the problem, ive been to about 8 different garages and all say different things its killimg me :/ I just had the egr valve cleaned and it was full of carbon but now drives a bit quicker but still smoking audi say they wanna chamge all 6 injectors but its mega money and all the other garages say the injectors are workimg fine?? Weird, anyway ive so far heard injectors, flywheel, lambda probe for the cat, egr valve and maf sensor lol already paid 150 euro to clean the egr but when do you stop lol, any thoughts please would appreciate any help.Thanks

[gupsterg]

I've seen a notification of thanks on the injector thread in there is info on just physically identifying the revision of injectors and dating their manufacture plus the TSB/TPI. If they are all old revision and car done a lotta miles it also makes it more likely they need changing IMO. There is also information concerning checking injectors via measuring block data in that thread.

When you said you had EGR cleaned was it the valve? cooler? cooling flap unit? I would really recommend removing the throttle body adapter and viewing the EGR gas inlet ports to see if they are blocked.

Link:- Post 236 of this thread have links to other threads concerning all the things I started doing to resolve the issue reading them may help you.

My fix was I disconnected the MAF, this forced EGR off physically and made engine ECU default to using different calculation method for air mass from what I understand. I have now be driving it around for a couple years like this. Read posts where people highlight disconnecting MAF causes poorer fuel economy but in my case seemed the same and I don't use DIS to calculate MPG.

Yes I have MIL on dash from doing this, every year for the MOT I reconnect MAF so tester doesn't spot its disconnected. I remove the vacuum hose to EGR valve to keep it closed and place a UK plug fuse in it to seal vacuum system back up. I clear the MIL on ins.cluster with VCDS and the MOT tester never removes engine cover so never sees fix, the associated DTC for lack of EGR flow never occurs for several cycles of engine on/off and as no MIL car passes MOT, later I revert car back to my fixed state.

I do believe I need to do further work on EGR/intake and perhaps I won't have to do what I do to keep car idling normal and passing MOT but I really couldn't be bothered to plough more time, money and effort to sort the issue properly.

I do wish you luck with resolving your idling problem and hope it is an easy fix, feel free to private message for anything useful I can share out of my experience of this fault.

[Danodrisk]

Hi, thankyou for your reply, seems as though you came to the end of your tether trying to sort this problem, but im guessing like me you would like and expect your 'audi' to drive near perfect lol regards to the egr cleaning, im not sure wat they did, with them been german its hard for them to explain to me other than they 'cleaned' it. I disconnected the egr pipe and the shaking stopped for a day but now its back again, sometimes with an even more harsh idle on startup with the Rev pin jumping around, it scares me really mate cause none of the garages seem to know tue problem and all keep suggesting doing different things but where do you stop forking out for jobs that arent gunna do anything :/ im really tempted to change the injectors

[gupsterg]

Yes did expect more from this car and I don't think my expectation was too high. I sort of got to a point where I needed to stop for my sanity and bank account!

If in your shoes I'd invest in VCDS, then you could view the measuring blocks in engine module for air mass / injector calibration.

VCDS for me paid for it self very easily, besides some of the retrofits I did to car I've used it to do oil service resets every year, twice used it for rear pad changes and loads of diagnosis work.

Genuine cable is more expensive than the clones on ebay but you get great email support, ross tech also now got a great forum plus free software / firmware updates to VCDS.

[Jazzy Joe]

It is 2020 and I think I came to the bottom of this on my 2006 199kW ABT tuned A6 (BMK). My symptoms are as follows:

• Occasional (every month or so) hunting/surging revs at idle
• Mostly after a refuel
• The surging is even (a 1-second phase and 100rpm amplitude), it takes around 5-7 minutes, then stops and the revs are perfectly level
• The surging stops immediately after disconnecting the MAF

I noticed one very interesting sensory phenomenon during the hunting/surging phase. The smell of my exhaust gasses and the crackling of metal when I cut the engine right after is reminiscent of the smell and crackling exhaust metal after a manual DPF regen. This smell is very hard to describe if you’ve never done a manual DPF regen (a very distinctive smoldering/burning smell and immense heat from under the vehicle).

Another very interesting thing is that I NEVER noticed the DPF regen indicator light up on the dash for the entire time I’ve owned the car, and yes, the car comes with a DPF filter. I assume the car does the regen on long motorway runs, but in my case it has never entered the DPF regen mode signaled by the dash indicator. For this reason, I do the regen manually every year or so to stay on the safe side. The car is in use every day.

Therefore, I contest the “hunting revs” issue is actually a DPF regen sequence on this specific iteration of the BMK engine. It smells the same, it stops after a while, the car drives beautifully with no other issues, it is occasional, and it stops when the engine management system is tampered with (MAF).

[Jazzy Joe]

Hmmm. I fixed it After years of living with it -- or even accepting it as a "feature" of this A6 model.

It WAS the DPF! Had it cleaned professionally and replaced the differential sensor (plus the relevant VCDS coding). The new reality: no hunting revs when hot, no itchy smell of fuel.
It makes all sense now. The ECU was trying to regen a partially blocked DPF filter by injecting more fuel.

And how I found out? I measured and logged the MVBs in the 100-104 range and noticed a bunch of consecutive silent regens (no dash light) per drive cycle that correlated with the rpm surges. The MS Excel "Analyze Data" function was very helpful in this.