V6 A8 Misfire
 

Please first see my posting of 7/23/2005 about this misfire.
Two years on I still have the car and the misfire. Now almost everything has been changed except the motor itself! It has a new ECU, GCU, cruise control CU, injectors, HT coils and leads, all the switches/detectors like mass air flow, oxygen and the like and it still misfires! We have considered other causes like wheels and tires and drive shafts and all have been changed or checked. Briefly again, the problem isat low engine speed <2000rpm and very light throttle pressure it feels like it is running too lean and is fluffy and juddery, give it more throttle and itpulls awayperfectly but around town at low speed it is totally unacceptablefor a car like this, even passengers can feel the misfire/judder. Everybody who triesthecaragrees it is not right including Audi but when they could not fix the problem they sent me away sayingthe caris in spec and if I did not like it buy another car!!
I have convinced myself that the car is in spec but the ECU fuel profile has been setas lean as can be for fuel economyat this low engine speed/throttle setting and on my particular car it is just too lean. Hoping I could fix itI had the ECU "chip tuned", The outfit that did it said they dont change the fuel profile but I thought maybe it would help.The chip tunemade a very marginal improvement to the pick up but it did nothing to improve the misfire.
My question now is:-has anybody got experience of making more radical changes to the ECU thana simple chip tune, maybe someone out there has the Audi software for the ECU and maybe had experience with it during development or in the aftermarket formore serious tuning.
It is disappointing that in two years nobody has posted a response to my original question about this misfire, surely my car cannot be the only one with this problem and somone out ther must have had a similar experience!

RE: V6 A8 Misfire
 

you can get a free down load from revo called lemmiwinks if you do a search. alot of times you will be able to find it on vortex forum. then buy a vag com cable and you will be set. you can change alot of different peramiters.

here is a guide for lemmiwinks.
this is the link to download lemmiwinks http://www.ecodetuning.com/revo/Lemmiwinks.exe

good luck!

RE: V6 A8 Misfire
 

If your getting a miss-fire thats that hard to diagnose i would say it has to do with the engine wiring harness. I've found on several different cars the when the harness runs under the front bulkhead the insulation gets cut (the bulkhead is sharp) and causes a short to ground. It could throw everysingle fault imaginable from a short to ground on the injectors, to running lean.
Trace the harness under the bulkhead and feel around there (you probably can't see it) and see if you can find any frayed wires.