Audi A3 1.8 T-sport - Rough Idling & Running

[philboy]

Hi,

The girlfriend has an Audi A3 1.8 T-Sport which I occasionally drive. Recently it has been running rough at idle in the cold and has the odd hiccup after it's warmed up as well. Doesn't seem that bad at the moment but you lose confidence when pulling out of junctions and feel that it may let you down. She's had a lot of trouble recently with the engine warning light coming on and several trips to the garage have fixed this for about 2 weeks before it comes on again. It's a 'Y' reg plate by the way. Does anyone have any ideas what could be wrong?

Thanks,

Phil

[skelly]

I also have a A3 1.8t with a similar problem. I have spent around £700 over the last year trying to sort this out. it has always been worse in winter or when cold, it starts fine but as i pull away the engine misfires and does not pick up properly unless i give it plenty of revs (about 3000). It gets better when it has been running for about 15 minutes and only really does it at low revs in first and second gear when you put your foot down. I have had it diagnosed and two problems showed up. The first was a problem with the waste gas gate (the turbo dump valve). This was replaced and a second fault code showed a pressure drop between the turbo and the throttle body (someone at an audi garage told me it could be a cracked throttle body) but the garage pressure tested the system but could not find a leak. After cancelling the fault codes all seemed ok for a couple of days but then the misfire started again. Someone tipped me off about similar problems with the air mass flow meter but i have had it changed twice in 12 months so i don't think it is that. I had it in at the garage last week and they looked inside the turbo and found a butterfly valve that was well worn. They said it would cost about £400 to replace and would improve the turbo boost pressure but could not guarantee that it would solve the misfire problem so i am reluctant to shell out again. If anyone has any other experiences of this then i would like to hear from them. (sorry about the essay but this is really bugging me now). Skelly.

[philboy]

Hi Skelly,

Thanks for your reply. What you have described seems to be exactly what we've noted. It seems fine at speed but when it's cold and driving round town there is a definite problem. Sorry to hear you've spent so much. We've spent about £150 so far: It was sorted a couple of times by a local friendly independant garage but then the problem came back. We then took it to the local Audi dealer (with £50 per hour labour charges) and they fixed it for 2 weeks before it came back again. I don't have any confidence in Audi's ability to diagnose and fix this and so we could spend a lot of money trying to sort this.

I read somewhere about 'coil packs' on Audi's and VW's and that there were some replacements made on cars that had similar problems to what we are seeing. I was wondering if it was that problem and whether to go down that route. Do you know anything about that?

Regards,

Phil

[RickT]

I faulty coil pack would/can cause a misfire... but that would be logged in vag-com advising that and also on which cylinder...

I had a simliar issue with it running rough about 9 months ago.... (non turbo) in the end up it was a leak in the air flow after the air flow meter and a leak on the vacum pipe for the brake servo - replaced these parts and all fixed! when the engine was running listen to see if you can hear any air been sucked in??

In regards to Audi charging you £50 per hour... thats cheap weres that!!! (audi up here charge £105 per hour labour. what ever the issue.)


Cheers

[skelly]

Thanks for the pointers but i've had a quick look (and feel) and can't see any sign of a split hose. Someone else has mentioned about a lambda sensor. Does anyone know what this is and how i could find out if it is this?

Another question - i've seen people refer to vag-com, what is this?

Thanks

Skelly.

[T-sport]

skelly the lamda sensor is a sensor that is normally found screwed into the catalytic converter on the exhaust.i think it is designed to sense the air and fuel mixture from the engine and could cause rough running problems if faulty.I had a friend who had a faulty one on his car and it caused all sorts of problems when he had his mot test as it affected the emmisions from the car.

[T-sport]

vag-com is the computer software audi/volkswagon group use to diagnose faults with there cars.they basically plug your car into there system and the cars computer identifies any faults by way of codes that then show up on the software.