Out of ideas

[mstirlz05]

Hi folks

For the past year my a3 1.8t has had intermittent misfires/rough idling issues. The first time it happened I took it to a garage and have no idea what they did but it cost £40 and ran smooth as silk after.
A few months ago the same issues happened, and, after some research, I unplugged the throttle sensor plug, DC the battery, re connected, and the problem was sorted.
Then the other day, after hastily pulling out of a car park with the engine cold, it started to miss again.
I found a possible remedy for this, which would be taking out the MAF sensor and cleaning it with contact spray. This I did, and the moment I had a look at it I had doubts as it looked fairly new. Sprayed it, and there was no dirt come off whatsoever.
While I was doing the work I checked all the vaccum hoses, and every one is fine with no cracks/splits.

The stage Im at now is as before. When the MAF sensor is plugged in, it is rough and misses, and when I un plug the MAF sensor, it stops misfiring but still idles rough and feels restrained when I drive.

Sorry for rattling, just want to note everything I have tried so far. If anyone may no a cause for this I would be uber grateful

Thanks in advance.

PS, coilpacks were changed by audi and car is due for service in next 1000 miles.

 

[Greg-S3]

Have you checked the throttle body? I often fun a clean and a throttle body reset helps with poor running issues at work

 

[TDIQ]

Have you had it scanned with VAG-COM? That's the first thing that you should do as it may have logged a fault which will let you narrow down the problem.

 

[mstirlz05]

Gregor s3- I did a TB clean on it today, but I am sure it is an air problem, as, when I plug the MAF sensor in, it runs crappy, and when I unplug it, it runs ok but not great. I had the EML appear today, and the MPG dropped to 25!!
After DC the battery and re connecting, the EML went off and MPG started rising to normal again.

Either way I may have found the problem. When looking round the engine I noticed the hose that delivers air into the block itself (dont know the name of it) has a split in it. This leakage of air could be causing the sensor to send false readings and cause misses.

Aaron TDI Q, I cant put it on VAG COM as no one has it in my area to my knowledge.

 

[<tuffty/>]

Is this an AUM or AGU engine code? makes a difference when trying to help diagnose your problems...

Have you looked on the VCDS map in the VCDS section?

<tuffty/>

 

[Greg-S3]

Is the pipe your referring to part of the breather system?

 

[<tuffty/>]

If its an AGU then unplugging the will be the reason its running crappy as AGU's use the MAF for everything... if its misfiring then it could well be the ignition control unit... typically its cyl 3 that misfires with this fault and is a very common issue...

Unplug the injectors (electrically) one at a time and listen for a change in engine note... the cyl you unplug that doesn't change in note will be the one misfiring..

<tuffty/>