[Audi A3/S3] Random Idle on 2.0TDi 170 A3

[C_bukowski]

Someone mentioned this elsewhere- engine increases revs in order to generate heat in order to burn off excess fuel additive deposits from the diesel particulate filter.

[edo]

Perhaps you arent driving it hard enough!

[philpatton]

Just a quick post to keep folks up to date on where I am with this problem. I booked the car into Doncaster Audi today for a diagnostic on the random idle and jerky ride. I took the master tech out for a run up and down the M18 to find that the problem showed itself.

The master tech recalled a problem he had with a demo car which displayed the same sympoms, and was cured by replacing the ...............turbo!!! The regeneration cycle of the DPF appears to be a red herring, as it cannot do it unless the car is cruising. It is more likely that there is a leak and the pressure from the turbo is venting to atmosphere. This causes the engine to increase the revs to compensate.

Car is booked in, so I wil let folks know how it goes.

Also, he did mention that supermarket fuel is not the best in the world, and with the 170TDi being rather highly tuned, it only wants quality fuel.

[Vertigo1]

Hi again Phil, how did you get on with the car in the end, did they confirm it was the turbo or are you still scratching your heads?

I'm no further along. My dealer has speculatively replaced the EGR valve but to no avail and is now out of ideas. Somewhat comincally, after months of having to describe the problem to puzzled staff and not be able to replicate it whilst in their care, one of their 170 TDI A4s has now started showing the same problem!

It's definitely the 170 engine that's the issue as I've now seen reports of this issue in A3s, A4s and Golfs with this engine.

Would be very interested to hear how you've got on recently.

[Vertigo1]

Update on this for you all.

On Wednesday I had my local dealer update the software on the car to see if it had any effect and, whilst they were at it, they discovered the exhaust gas temperature sender was reporting odd readings so they replaced that too.

Lo and behold, the car went into a DPF regeneration cycle on Saturday morning but it wasn't accompanied by the tractor noise! Audi had already incontrovertably linked the noise with the regeneration cycle and this is often accompanied by a raised idle which I saw on Saturday morning so I knew the regeneration was taking place.

If I turned off the radio and listened carefully I could tell something was happening as the engine was making fractionally more noise than normal but it was but a fraction noisier and a world apart from the racket I used to get. Looked like either the update or the sender replacement had fixed the problem although I am reserving final judgement for a while until I'm sure this wasn't a freak coincidence.

Critically, I've just had an email from Powerphil saying that, although the turbo replacement had no effect, he has also had a very similar sounding part replaced on his car and this has also solved the problem!

Looks like we may have found the culprit. I'd suggest everyone with this issue gets in contact with their dealer and pursues replacement of this part ASAP.

[karim.hady]

Hi all,

reading you guys posts has been very informative, however my dealer has not come up with any solution except "put some redex in and give it a good thumping!" which i did not do as i have been told that it does more bad than good.

My audi a3 2.0tdi sport rumbles when stationary when temp is norm and cold, also my idle never sits still, always raising and falling slightly......however i do not notice any unusual sounds except the obvious increase in engine noise when the car is cold and is first started.

any ideas...? :confused:

thanks in advance

audi a3 2.0tdi sport (remapped to 175bhp) 83,000mls (last service 79,000)