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

[sparker]

Thanks

Nice clear understanding of EGR, EGR cooling and of MAF sensor and what it does. How all this communicates, works together and the test you are doing is the tricky bit!

Rooting for you to find a cheaper fix.

Still interesting read and great research.

[a8 tech]

its simple

isolate egr fault gone

trace egr system for mechanical error (leakage) and double check throttle body operation

egr ok trace back to injectors/fuel pressure dwell angle (point of injection)

failing this the actual point of injection is critical to see egr/air/fuel

take into account worn camshafts etc and worn injectors/pump

what can we do, well with a decent remapper its possible to alter the idle tolerance for fuel/egr/air

without dpf and egr i would suggest this issue would not occur but we have these devilish add ons so to work within in tolerance on a ageing engine with soot build up etc then irregular idle will occur as the combustion process is effected by dirty air (egr bounce)

good luck

[sparker]

Ok, now that does make it easier to understand.

Many thanks a8 tech.

[gupsterg]

Hi A8

Some advise please I have not yet found info... so when MAF disconnected EGR cooling is off can see that...

But what is the EGR valve defaulting operation to? ie fully closed as can't view that

But when MAF connected is EGR valve trying to adjust, but as could be failed sending things to pot?

I know not same as the valve on 3.0... I've been looking at this video...



I know I have no DPF... but are you saying at 80k my problem is normal issue which happen or you see regular on these engines?

Are modern engines not getting to the mileages that past ones did?

[a8 tech]

use a mitivac tester to make sure
Mityvac Silverline Elite Hand Vacuum / Pressure Pump

a. the unit opens and closed
b. holds vacuum

you can also see in mvbs the egr operation whilst operating via the mitivac so a full picture of open and closed can be assessed

the duty cycle can be seen also and this is pulse width signal from the ecu ultimately controlled via airmass and coolant sender readings

Driving Vibration Motors with Pulse Width Modulation | PWM Signalling

if you do not have dpf i can give you a software update that will sort this out

[a8 tech]

I know I have no DPF... but are you saying at 80k my problem is normal issue which happen or you see regular on these engines?

Are modern engines not getting to the mileages that past ones did?

modern engines are fine but dpf and egr can make for some interesting issues

anyway see pm for software update that should fix it if your vehicle does not have dpf

[gupsterg]

Cheers for research A8 Tech

Will book ASAP and see if they can do SVM for my J519 as well Link:- Replacing onboard Supply J519 / Leaving Home Lights

I did create a restricting plate using a large flat washer (38.5mm Link:- Halfords )and dremeled the ends to allow the bolts on EGR connecting pipe...



So washer in place, MAF connected... when car started it still idled rough... but sorted it self quicker... whilst running I disconnected MAF and I noticed a change in engine idle noise... more smoother... the moment I connected MAF I could see the slight rocking and uneven idle come back... besides undoing the EGR connecting pipe at the throttle adapter on the top section of intake manifold... I had to undo the the manifold to allow movement to add plate... one thing I noted how quickly washer discolour... what bad effect EGR must have on engine

I did not go for test drive as I felt idle not smooth so what the point...

But on a lighter note Zesty the A6 has passed MOT without any advisories

[OddBallBoy]

'Liked' for passing the MOT at least!
Still feel for you on the rest of it though.

[gupsterg]

The nuttiest thing is last year as well when MOT was due she pass without a single complaint... if anyone wandering how come two MOTS in space of year? well when I got car it had 3mths or so MOT on... I didn't push selling garage to pop one on as I thought car OK... plus don't know if they could or not ...

[gupsterg]

Well been to Audi today... service advisor listened... searched and said computer say no to TPI for ECU update...

He said he will book in for next week... get a technician to view car so if doable or not... Ahh well

But on another note found an A6 which could be Zesty's replacement

MAF/THROTTLE look good from tonight's run with MVB 07 10 18

May ask an indi if they can test EGR valve... or ask Audi when they have...

So will update what happen...