revs racing intermittently then black smoke

ewaned · May 30, 2015

Can anyone give me advice on this. 2005 a4 cabriolet 2.5 with 100 000 miles. When driving the revs will increase without warning then dips back again and will keep doing it for a while. Sometimes it's followed by a release of black smoke. I took it to a diagnostic shop but they couldn't be ar... as there was no fault showing on the computer. I don't know what to do now! Has anyone had this problem. Thanks.

Administrators · May 30, 2015

Could be oil.... Your car runs on a very thin oil (i'm guessing it's the 2.5Tdi 163) and if enough oil builds up in the intake pipes and then gets drawn into the engine it would cause the engine to rev and make lots of black smoke. Or it could be a small air leak.

Check that the oil isn't overfilled, See if there is a large amount of oil in the intake pipes. Have a look at all the joints on the pipes from the turbo to the intercooler and then to the engine.

Just one other thought, I have see clutch switches cause a similar problem but not seen it on the 2.5Tdi.

If a Diesel runs away it can be quite something

ewaned · May 30, 2015

Thanks for that. I wouldn't know where to start but I'm going to ask the local garage to do it. I like the car and I want to get the bodywork tidied up and alloys done but I'm worried about doing that until I get this sorted. Thanks again.

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revs racing intermittently then black smoke

ewaned

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ewaned

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