Asking for advice re 06-plate A4 TDI S-Line with lots of sooty smoke and no oomph

**jangles** · 06-05-2012,07:32 PM

I've read lots of threads here about this issue that I experienced today - sudden loss of acceleration, lots of smoke from the exhaust, hard to get above about 40mph even with the pedal to the metal.

I was in Sussex today, about 70 miles from home. On the drive there this morning, nearly at the destination, I experienced the first of this hiccup: sudden exhaust smoke, loss of power. No warning lights lit up, nothing alarming experienced, other than that.

At my destination, we inspected under the bonnet, especially the intercooler (based on other threads here). Nothing visible: no oil deposits, no leaks, no broken or split hoses, nothing untoward-looking at all. Oil at max level. In any case, the exhaust smoke was sooty not oily.

So the journey home. Started out just fine but in between Gatwick on the M23 and the M25 junction, lots of smoke and loss of power causing me to pull onto the hard shoulder. Switched off, waited about 10 mins (yes, still sitting in car, not a good idea!). Started again, but as soon as I engaged drive (it's a multitronic box) and tried to pull away, the engine stalled. Engaging drive, btw, produced the usual 'OK' in the dash display.

It wouldn't let me drive. The engine started just fine, no smoke, normal sounds and tickover about 900rpm as usual.

So I turned off the engine and called the AA.

The AA man arrived about 45 mins later. He inspected under the bonnet, found nothing amisss. He started the engine, revved it at very high revs. Huge volumes of sooty smoke to start with, gradually diminishing.

Bottom line: nothing wrong per se, it seems, but obviously something amiss with this issue. So I drove gingerly home. 'Gingerly' because I could not drive faster than 50 or 60, much less going uphill. I guess this must be the 'limp mode' I've read about elsewhere in this forum.

Most of my journey, I drove in sport mode in order to keep engine revs much higher than usual, between 2500-3500rpm. AA man advice. After starting off from the M23 roadside, I didn't notice any more sooty smoke from the exhaust, but certainly did experience limp mode.

Anyway, I plan to be at my usual Audi dealership in Reading on Tuesday morning to see if they can diagnose what's wrong. The car has been serviced throughout its life to schedule by an Audi dealer. I've had the car since Oct 2010, some major work done since then, all at Reading Audi, incl new timing belt, DMF, aircon compressor. It just (today) hit 100K miles. It's in between a long-life service. It's in pretty good nick!

I'm aware of soot issues with diesels and the need to burn off deposits. My driving is a mix of motorway cruising (usually M4 into London) and suburban driving at the speed limits. Nothing unusual; I think how I use the car is good for deposit burn-off. Sometimes I'll drive for 15-20 miles at high speed in sport mode, just to keep engine revs really high that might aid the burn-off. But maybe I'm wrong...

Any ideas or thoughts on what the smoke and limp-mode issue might be? No doubt I'll find out on Tues but it would be nice to think about it (and possible implications and costs) beforehand.

Thanks.

**a8 tech** · 06-05-2012,08:51 PM

air leak, lower turbo pipe

intake manifold change over valve vacuum leak off causes a drop of supplied vacuum to the turbo

vacuum pipe collapsed or hairline crack

black smoke = air leak or air intake blockage

**jangles** · 06-05-2012,09:14 PM

@a8tech, many thanks.

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**Boxa786** · 06-05-2012,09:16 PM

Happened to me exactly what you have described and was escorted home by AA. took it to garage next day to find it was the EGR valve. A small bit had actually split but lucky for me non of it went in to the engine.

**jangles** · 06-05-2012,09:24 PM

@boxa786, thanks for sharing that experience. The EGR valve - that's the possible cause I've been wondering about most.

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**a8 tech** · 06-05-2012,09:29 PM

yep could be egr flap or the egr cooler pipe split lol lots can go wrong with these

good luck mate

**Boxa786** · 07-05-2012,11:43 AM

no problem jangles, hope you have it sorted soon mate.

**jangles** · 07-05-2012,12:29 PM

Thanks @a8tech @Boxa7856, appreciate the support

I'll add an update to this thread when I know what's happening and how much it's going to cost...

**MFGF** · 07-05-2012,10:40 PM

I started reading and immediately thought "broken EGR valve", because I had the exact same symptoms on my 2005 A6 2.0 TDi. In my case the flap had parted company with the spindle inside the valve. I have never seen a car chug out so much black smoke!! I was away from home in Bracknell at the time, and the car was recovered to Slough. No faults were logged, and they changed lots of parts before finally looking at the EGR valve.

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