2002 audi A6 diesel - exccessive smoke

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Sun 10 Aug 2014 18:56
2002 audi A6 diesel - exccessive smoke - adrian19

My Audi A6 has put a lot of black smoke since I bought it new. retuned to Audi numerous times to be told nothing shows up on the diagnostics, so had to put up with black smoke and approx. 38 mpg. eventually left it at Audi and said do not return it until it's fixed.They eventally returned it having replaced the egr valve. I then had 40mpg. Audi carried out the first MOT but did not give me the exhaust gas analasis, when asked for it they said it would follow. it never did. I then had MOT's carried out away from Audi, each year it just scraped through, now 12 years on with 97000 miles the car just failed latest MOT on exccessive black smoke, I have removed and cleaned the egr valve but still smokes when revved up a bit. the car starts instantly and still performs well with 42 mpg. Any ideas about the smoke.

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Sun 10 Aug 2014 21:35
2002 audi A6 diesel - exccessive smoke - double_tap_that

Back to basics but have you tried replacing the glow plugs?

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Mon 11 Aug 2014 09:21
2002 audi A6 diesel - exccessive smoke - Railroad.
Black smoke in the exhaust means excessive fuel or insufficient air. The latter is much more likely. You've already said you replaced the EGR valve. In so doing you couldn't have failed to notice that it was coked in thick black soot. They always are. That being the case has it occurred to you that the whole air intake downstream of the EGR valve will be coked in exactly the same way? The manifold needs to be removed and cleaned. This thick black sludge is restricting the engine intake air flow.
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Mon 11 Aug 2014 12:19
2002 audi A6 diesel - exccessive smoke - galileo

The OP does say it has done this since brand new, when the manifold should have been clean, maybe it's just a characteristic of this particular car and its tolerances?

Cleaning everything should certainly help minimise smoke, I suppose its a personal judgment as to what is 'excessive' anyway.

Edited by galileo on 11/08/2014 at 12:25

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Mon 11 Aug 2014 13:38
2002 audi A6 diesel - exccessive smoke - Peter.N.

If you normally drive it gently it could be accumulated soot in the exhaust system, its always good to give it a high speed blast on the way to the test to clear it out - I have this problem with my cars.

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Mon 11 Aug 2014 15:36
2002 audi A6 diesel - exccessive smoke - dieselnut

Being 2002 model this should have the 1.9PD, an efficient unit & not renown for smoke.

My wife has a Passat with the same engine & would expect something to be wrong if we didn't get well into the 50's MPG on a run over 10 miles. But it will also depend on how you drive as well.

Her car has 130k miles on the clock & I removed the EGR for a clean for the 1st time recently but it wasn't unduely caked up with soot.

You really need someone with VCDS to scan live data & see what is out of kilter.

The water temperature sensor is a common failure & would cause a richer fueling if failed. They have 2 sensors in one. One output connects to the temperature guage while the other connects to the ECU which controls the fueling. So you can only look at this via a diagnostic like VCDS.

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Mon 11 Aug 2014 15:44
2002 audi A6 diesel - exccessive smoke - skidpan

Has the car been fitted with a tuning box or similar. They have a tendency to make casr smoke.

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Mon 11 Aug 2014 17:52
2002 audi A6 diesel - exccessive smoke - adrian19

Hi, the car is standard, 130 BHP

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Mon 11 Aug 2014 17:48
2002 audi A6 diesel - exccessive smoke - adrian19

Thanks for the reply, I have replaced the water temp. sensor but has not made any difference. I will strip the intake system as someone suggests but this has happened since new and would have thought it would have been clean in the ealy days

On the german autobarn at 100+mph it actually returned 50mpg.

Lincoln Audi are not and have never been interested.

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Mon 11 Aug 2014 17:42
2002 audi A6 diesel - exccessive smoke - adrian19

Hi thanks for the reply, most of my mileage is on the moterway and I dont hang about.

The best mpg was on the German Autobarn at 100mph plus it then returned 50mpg.

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Mon 11 Aug 2014 17:39
2002 audi A6 diesel - exccessive smoke - adrian19

Thanks for the reply, I call excessive when it fails the mot due the excessive emisions

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Mon 11 Aug 2014 17:37
2002 audi A6 diesel - exccessive smoke - adrian19

Thanks for the reply, the EGR was replced under warranty at 5000 miles as it was completly choked. I did ask the sevice manager if this was normaland he didn't seem to comment on the subject, I thought there was somthig wrong if the EGR valve was choking up. I have little faith in Lincoln Audi. I will strip intake system to see if there is any restriction. I will let you know. The only time I had a better fuel consumption aws when on holiday tourig Germany on the Autobarm,running at 100+ mph I had a return of 50mpg.

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Mon 11 Aug 2014 17:29
2002 audi A6 diesel - exccessive smoke - adrian19

Thanks for your reply, but would this not happen only when cold if the glow plugs were faulty. This happens all the time even when hot.

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