Running a little Lumpy????!

[bigselbs]

Can anyone help? Went up north, weekend just past and found on the return journey the car was a little lumpy in places. The only way to describe it is that as you accelerated it fractionally lost power(stuttered) and then whack... all the power came is as requested.
I've no lights or errors coming up on the dash and it is intermittent. Yesterday car proved to be fine but tonight on the way home from work it happenned again albeit briefly.
It''s happenned when the car has been hot and marginally warm, although I could understand the temperature having something to do with it after a cold start up?? However, it did do it on occasions over an hour in the motorway trip back?
For the moment all I can do is keep an eye on it and see if it can be reproduced.
Anyone any ideas where this may be leading?
Thanks

[kaisersolsay]

What kind of car is it mate?

[bigselbs]

Std B6 S4 Avant Manual

[tuscy]

I've had this happen to me too. Probably only 5 or 6 times in over a year and it's not done it for the last few months.

It only ever happened in the same place on my regular journey back from work, after 15 mins on a dual carriageway I'd turn off left at a roundabout. It was always while accelerating off the roundabout, just as you say, slight hesitance and then the power suddenly back again. Pretty sure it only happened in 3rd gear too, don't think it's happened in 2nd.

Had Audi check for faults at the last service and nothing is showing. I took it as a minor bug in the ECU mapping causing a glitch when a very specific condition arises. It's so rare that I'm not bothered by it.

[audi24guy]

It happens to me every morning on my way to work, engine still cold and accelerating fairly quick in second, minor loss of power for a brief second at around 3 to 4000rpm. I havent experienced it in any other gear. I have cold air intake, exhaust and ecu chipped, not sure if that would cause it.

[bigselbs]

Well it finally gave up today! Started misfiring just as I turned up to work. Engine warning light came on and started flashing. Car stank of fuel and was rather smoky. Called Audi Assist who were there within 20 mins, diagnosed fault as dodgy coil on cyl 4, said they could fix. After testing coil tech said it was injector wiring problem and therefore needed booking into dealers.
The cars in the dealers and they called and said they need to replace bits on the injector? and also the ecu!
Glad to say that both audi assist and delaers have been very good.
Anyway, will let you know the final diagnosis when I get it back tomorrow , fingers x'd. Dont fancy the prospect of long distance journeys in the loaner.... Vectra diesel uurrrgh.....

[bigselbs]

Thought I would just let anyone whos interested know the outcome of this one. Dealer called to say that its all fixed and ready for collection. Diagnosis was that the wiring to the injector was to blame and car thought it was misfiring and as such it started to overfuel the car on Cyl 4. They've replaced the injector, injector wiring and also the ecu. Not being tehnically minded I don't know if this was a big job or not but its fixed!
Must say, in my 6 months of Audi ownership, the service I've received to date has been really good and some other premium brand dealers should take note.
Happy Xmas one and all

[jamess4cab]

My car is doing this at 1800rpm at the moment - just a minor blip and then pulls well after that.

I am putting it down to the std unleaded I have had to use to due to svereal stations being out of super. When i get it back on super, is there anyway to reset the ECU as on my Porsche, the ECU would reset to adapt to std, but then not change back for super???

[BlingBling]

S4 ECU will eventually adapt to the change in fuel octane.

[jamess4cab]

S4 ECU will eventually adapt to the change in fuel octane.

Thanks for confirming that???

Is there anyway that you can just reset - e.g. disconnect the battery and then restart the engine??

[BlingBling]

Why would you want to reset the ECU?

[jamess4cab]

Why would you want to reset the ECU?

Cos once I have a full tank of decent fuel and not std unleaded, I want to reset the ECU for 98/99 RON. It worked perfectly on my Porsche.......