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

**gupsterg** · 23-10-2012,04:07 PM

What data you need A8? thanks..

**a8 tech** · 23-10-2012,04:18 PM

None at the min just need to confirm if the egr side is ok, this is part when vas pc is far more powerful than vcds

So if the throttle valve is now resolved the next step i would take is to reduce the egr flow at the intake on the throttle valve by using a blanking gasket or reducing the diameter of the port hole

This will reduce the flow and again you could test it or check the egr is order (I think its leaking through when it should be off) or back to the worn injectors poor spray/dribble

Rule egr out firstly

Vcds is just a glorified reader and limited in diagnosis or actual data to aid you, as you can tell not a big fan of vcds its primitive and becoming more and more useless for diagnostics after 2008 (for me anyway)

To aid you gfs light may give you far more info than vcds or ross tech wiki

I have vas, cost me a lot of money (not the pirate clone copies) but essential

You don't have to keep thanking me, its flattering but its hardly a glamorous job fixing cars more like a prison sentence lol

**gupsterg** · 23-10-2012,04:31 PM

Throttle valve is new... now...

Any suggestions as what to use... I am geek turned mechanical

**a8 tech** · 23-10-2012,04:40 PM

blank off at the charge air intake manifold port

make sure the egr cooler vacuum unit is working as well

**gupsterg** · 23-10-2012,05:09 PM

So gonna have cuppa... check to see if I have something appropriate to use as blanking plate to constrict EGR flow where it meet throttle adapter connected to top section of intake manifold... if can't leave till find appropriate item...

May then go out and connect MAF... run car from cold to view what go on at EGR cooling flap/valve/vacuum unit and when at right temp/ revved etc...

As now the geek in uncharted skill territory

**gupsterg** · 23-10-2012,06:42 PM

I could not find anything to constrict the port... I connected MAF up... start car issue there

... went for drive got her up to 70c as SSP said you need higher temp than 60c for EGR to kick in and idling no more than 2 mins...

So vacuum unit working IMO... control flap arm in video no play...

**apole** · 23-10-2012,07:28 PM

Hey Gup,

Firstly well done with not giving up and being so patient, take my hat off to you for keeping on, and sharing your learnings as you go.

An idea on the blanking plate, may or may not be a good one !! What about carefully opening a drinks can, using paper as a rough template around the connection, then using that to cut around the coke can. Obviously it needs to be fairly flat and clean, and of course it's damned sharp stuff so you'd need to be careful and wear gloves but the ali is fairly easy to cut and soft enough to make a temporarly blanking plate?

Just a thought, something you are more likely to have lying around.

Does the car drive better with the MAF disconnected as well as not producing so much smoke out of interest?

Andy

**c4a5er** · 23-10-2012,08:12 PM

just be aware whatever material you decide to use to make this temporary restictor, if it breaks up due to vibration or heat it will end up being drawn into the engine!

**gupsterg** · 23-10-2012,09:20 PM

Hi Andy, I got no option mate.. I've test drove a 2.7 TDI FWD Multitronic yesterday... today a 3.0 TDi saloon... similar miles on clock to mine... both a year younger or older... they never had idling issue...Yes with MAF disconnected no rough/hunting idle... no smoke on hard rev in others headlights on exhaust...
Thanks for support and suggestion on blanking plate

so with help of A8 Tech and forum.. fingers cross will resolve...

Hi Chaser

These were the things I also thought about... so I thought better to take time to make... it would be handy to know what a good MAF ohms reading are... will check mine tomorrow when engine/maf all cold...

**gupsterg** · 24-10-2012,10:58 AM

OK some swotting up last nite first...

So the Throttle first... page 65 of Link:- EU5 3.0TDi SSP

Next MAF... page 57 of Link:- EU5 3.0TDi SSP

Next EGR... from page 30 of Link:- SSP 350

The vacuum unit from what I can tell is functioning and drives both the EGR Cooler control flap and EGR valve... I tried constricting@green box...

Some of the info above from the EU5 3.0 TDi SSP (the face lift A6 09-11) , Link:- EU5 3.0TDi SSP the other was Link:- SSP 350

So on above image the flap for deciding if EGR gas gonna be cooled or not is what I've tested... ref video post 106

So to test the EGR Valve (orange box) without removing it we must constrict flow (A8 advise) at point green box (I think this where he mean as I'm a geek

)

So a disfunctioning EGR valve if not sealing properly is letting wrong amount of EGR gas through when not needed... thus fuelling wrong and bad idle...

(my hypothesis from reading and thinking I'm understanding A8's posts please correct me anyone

)

Again this is also if MAF AOK... now ringing around for blanking plate... not found one but ebay have plenty...

Yesterday this video also aid in my swotting up...

Above is not the exact same setup as on the 3.0 TDi but show whats going on...

Done another test today... to see if it just in my head...

So no MAF connected... car start/idle well... lift bonnet and view... engine not rocking all look good... EGR cooling flap open so no cooling, do not know about EGR valve as no visual indication... the moment I plug MAF in... you can see the car engine start to rock... you hear the variation in idle... EGR cooling flap close to allow cooling as engine temp was over 60c... if you disconnect MAF it revert to no rocking... smooth idle... EGR cooling flap open again... all this test was done from one start up, engine running all the time, no reving just letting idle, car had been warmed to 70c ish...