'Fast Idle' On For Too Long

[Brian Robertson]

Can anyone please advise on the following issue which I have with my Audi A3 2.0L TDi Saloon (Feb 15) which I bought 'used' recently from an Audi Dealer in England.

With the coming of the colder weather I have been conscious, when starting from cold in the morning, of the engine running on fast idle for what seems to me to be an excessive length of time.

The critical outside temperature seems to be 7 degrees and whenever the temperature is that, or below, the engine starts in what I presume is the ‘fast idle’ mode, which holds it at about 1100 revs on the idle. The trouble is, this ‘fast idle’ is maintained for what seems to me to be a ridiculously long time. This morning when driving to work it was 18 minutes before the idle revs. dropped to normal and the engine Stop/Start facility operated. The temperature indicator had risen to 4 bars after 15 minutes (which I presume is ‘Normal’ working temperature) but still the engine stayed on fast idle until 18 minutes.

I should say that I am NOT running the car with air-con / headlights on etc. so it is not like the engine is having to rev. higher to cope with additional load.

My local Audi dealer had the car last week to put it on test but ‘couldn’t find anything wrong’; but neither could they give me an explanation of why it was happening. Surely there must be something wrong with it for it to remain on the fast idle for so long.

Could I ask if anyone else with this model has any experience of this?

Thanks,

Brian

[grant19841]

Did they not get any fault codes?

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[grant19841]

It be the coolant temp senor is faulty or the tps.

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[Brian Robertson]

Hi Grant,

When AUDI had the car in the workshop last week they said that no fault codes had shown up. Would a faulty coolant temp sensor show up as a fault? Sorry to ask but, what is the 'tps' ?

thanks,

Brian

[grant19841]

Throttle position sensor (tps)

A temp sensor will not show up, if it's faulty it tricks the ecu to believe its functioning and reading correctly.


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[grant19841]

It could be the outside temp sensor also.

Worth a mention to audi to see if the can check and test it.


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[Brian Robertson]

Many thanks again Grant. I'll take it up with AUDI again next week,

cheers,

Brian

[Brian Robertson]

Hi Grant,

I'm getting nowhere with my local dealer. I was in today to pursue this business of the 'fast idle' and I was dealing with the workshop manager. He refuses to believe that it is anything other than the Diesel Particulate Filter trying to regenerate itself and he is telling me to take the car for a long drive on the motorway. As most of my driving is in Edinburgh he is telling me that the engine will never get a chance to heat up properly, which I don't think is strictly true. This car is less that 12 months old and it only has 11000 miles on the clock, so I really wouldn't have thought that the DPF needed cleaned out. At no time have I seen the warning light come on so I fail to see how this could be a DPF issue. In any case, the handbook tells you the the DPF will keep itself clean 'with normal running'. I brought the car back up the motorway from Stockport last November, so I would have thought that that would have cleaned everything out then.

He FLATLY REFUSES to acknowledge any internet information which I got through a 'users forum' so he never even let me discuss with him your theory on the Coolant Temperature Sensor. I get the distinct feeling that I am being fobbed off but I don't know what more I can do.

I am prepared to take it for a run on the motorway but I honestly don't think it is going to make any difference. It certainly seems to me to be something to do with a temperature related issue.

What I really need is some other A3 TDi owners coming back to me to tell me how their cars perform when started on a cold winters morning. If their cars are doing the same as mine then I obviously have nothing to worry about. I have been grateful for your response but I am disappointed that I have not had any other feedback from A3 owners which would help me to decide whether I have a problem or not. I presume from the symptoms which I described at the start of the thread that YOU think the car is not running properly?

As the local dealer seems reluctant to do anything I wonder if I should take this issue to AUDI UK Headquarters,

thanks,

Brian

[grant19841]

Hi Brian,

Dpf do suffer from short journeys and sometimes they do take a little time to warm up,
See how things change soon.

Did they at least put the car on a vcds to monitor coolant readings etc?

They should at least of done that to put your mind at rest.




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[Brian Robertson]

I'm not sure what they did Grant, but I suspect it wasn't very much.

I called in today to a well respected independent VW/Audi garage here in Edinburgh and explained the symptoms. They are going to hook it up to the diagnostics and check the coolant sensors / coolant temperature / software etc. to see if it is anything obvious. They don't think it is anything to do with the DPF but they say they can check the carbon level in the DPF and give it a clean out in any case. I feel happier getting them to do it as I don't have any faith now in Edinburgh Audi.

The car is booked in for next Monday and I really hope that they find something. If they do I'll be straight back in to Edinburgh Audi to stick it right up them !

I have a good friend who has been a car mechanic for over 40 years (mainly Ford but he has worked on all types all over the years) and he was wondering if this is anything to do with the 'modifications' which VW have had to make to the Euro6 engine to make it 'compliant'. Could this 'fast idle' simply be something which they have programmed in to help to reduce the emissions? If it is something like that then why don't Audi just tell me that?

Thanks for your continuing interest and I'll let you know how I get on,

Cheers,

Brian

[Brian Robertson]

Hi Grant,

The car was in the independent Audi workshop today and it certainly got them thinking !

They ran all the tests they could; coolant temperature, coolant sensor etc. and everything seemed as expected. There were no 'faults' detected. They also checked for software upgrades etc. but there are none.
When they connected up the diagnostics however they did notice that the DPF had gone through a 'regeneration' process earlier in the morning. That was when I was driving the car to the workshop. I was aware of the higher idle speed during the journey, but this is what happens every morning when I start the car from cold (provided the temperature is below 7 degrees). I go through the same symptoms when I drive home at night, so it seems that the regeneration is happening every time I start the car from cold.

The technicians wired up their PC to the car and then took it for a drive. The 'ash' content in the DPF started at 16% but had dropped to 2.5% by the time they got back to the workshop. So it appears that the regeneration process was working even when they had the car out for a test drive. There were no DPF warning lights or 'fault' messages logged. The technician said that he wouldn't have expected the regeneration process to have started with the ash reading at only 16%.

They were certainly mystified by it all. Everything seemed normal; everything was within the expected parameters, but they can't understand why the DPF seems to be constantly regenerating. They couldn't come up with anything wrong but at the same time they felt that there must be something wrong for the DPF to be constantly regenerating.

Anyway, I'm going to get in touch with Audi UK to see if they can offer any technical guidance on this.

I'll update you if I get any more info.

regards,
Brian

[Brian Robertson]

Hi Grant,

I'm not sure if you are still following this thread but a lot has happened in the last few weeks, which I will now try to summarise.
The car was in at my local independent VW Audi workshop a few weeks ago. They confirmed that there were no apparent faults but that the DPF was regenerating EVERY time the car is started from cold. They couldn't explain this but they didn't think is should be doing this every time. They confirmed that the DPF was clean so the advice I received from my local Audi dealer (to take the car for a long run to clean out the DPF) was, as I suspected, a load of ********.
I took my case to Audi UK and, over a couple of weeks, received 2 responses from them regarding this issue. The upshot is:- When the engine is cold there are much more harmful deposits being exhausted from the engine, so it is obviously desirable to get the engine up to operating temperature as quickly as possible. That is why the engine idling revs. are higher than normal; it is simply to get the engine temp. up as quickly as possible. It is nothing to do with the DPF regenerating and, indeed, there is no link between the DPF and engine revs at all. Audi UK say that the regular regenerating of the DPF (at lower outside temperatures) is perfectly normal and will NOT affect its expected lifespan.
I e-mailed this info. to the workshop manager of my local Audi dealer and I managed to restrain myself from calling him an idiot. If he had given me this explanation at the outset then he could have saved me a lot of heartache and expense.
I hope that this concludes this matter and thank you for your help and advice,
best regards,
Brian

[grant19841]

Hi Brian,

Thank you for the feedback,
I'm glad in the end you finally got it sorted out after all the bother u had.

Grant

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[Oliver Head]

It's perfectly normal mine does it.

The reason is that the diesels have a 1kw electric cabin heater that comes on automatically when it's cold to head the cabin. The revs have to be high to generate the current.

It could also be doing a regeneration but that's normal too.