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A couple of weeks ago, I put some inferior petrol in the car and I noticed that it was significantly slower than before. I blamed the petrol, and after a couple of tanks of Optimax, was back to normal. But since then it has happened again?! This time on the same tank that it was performing well on!

It has only been fed Optimax since. So I'm assuming it's not the petrol. I also can't see how anything can be broken as it went from not working, to working fine for a while and then back again.

Anyone have any ideas?

MAF or coolant sensor are possibly culprets. they both can feck up fueling, hence performance..

How would i go about testing these?
Would this be the case even though it went from slow, to working fine (for a week) and back to slow again?

maf through logging data only, as it only gives ann error through total failure..

or some people run the car for a short run with it disconnected and see if it improves..

you can get a service exchange item from some audi dealerships at circa 70-90 quid.


Coolant sensor gives a fault code... but maybe not a fault light.

Mafs can be erratic, ive been lucky and never had a problem in my 2 s3's

Sounds like you'd be wise to reset the ECU. This will allow the car to adapt to the fuel again with any luck. Do a search on this as there are many theories on how to reset the ECU.

Cheers

Ben

Definately sounds like the MAF. Take off the 4 pin connector and give it a try for a couple of days. It wont do any harm. The ECU will recognise its not getting a signal and go in to a preset mode and the engine will run normally. A coolant temp sensor fault is an option but no where near as common as the air flow sensor.

Ash

Thanks people, it was the MAF, and runs much better now. Still not as quick as it should be though. How can I reset the ECU?

You need to use vag com or one of thw Audi diag machines. If your in Guildford at some point i'll do it for you!
07815 120363

Am near Brighton, but have a freind in Farnborough. If i'm up that way I might take you up on that.
Thanks for the help, appreciated.

Try disconnecting the battery neutral and leave it for a few minutes.

Try disconnecting the battery neutral and leave it for a few minutes.

Or unplug the ECU!

Seriously though, you should always clear down any fault codes that exist (and they will if you disconnect the battery or unplug the ECU) You will need VAG-COM to do this.

Nige.