Persistent slow start on 2006 A3 2.0 TDI?

**Fiend** · 19-11-2015,02:41 PM

I recently bought an Audi A3 2006 2.0 TDI 170hp DSG. It's generally great but has a persistent problem with a slow / rough start from cold, usually taking a few seconds for the engine to kick in if it's been left overnight / all day. If the engine has been on recently it will start fine:

The slowness / roughness of the start is in proportion to how long it's been left, although over 12 hours it's pretty much similar. If I start it like this (i.e. badly), turn the ignition off and on again, it starts a lot quicker.

The temperature has no effect whatsoever (5'C start the same as a 20'C start). How recently it's been running has the only effect.

There seems to be no effect from using the battery beforehand (e.g. listening to stereo, turning ignition on and off without starting).

There are no other running / stalling / juddering problems once the engine is running. It never fails to start.

...

I've taken it back to the dealer and had the following work done under warranty:

Fuel pump changed (there was evidence of contamination and oil seeping in, I've run through some super diesel with a fuel cleaner since then).
Fuel filter changed twice (before and after fuel pump change).
Glow plugs replaced.
New battery.
Dual mass flywheel replaced (local Audi specialist A4Audi and dealer suspected it could be this - blame them if it seems a ridiculous idea, not me!).
Also done normally: New cambelt (as part of standard 80,000 mile change).
Also the dealer checked with Audi and apparently the fuel injectors were replaced in 2013 under a general recall.

...but the issue still remains. I have it booked in to have a proper VAG-COM diagnostic (the dealer is a small general dealer and doesn't have vag-com), but any ideas in advance would be helpful.

...

Also, slightly off-topic, but the climate control is a fickle bugger with a mind of it's own: it keeps changing fan speed even when *NOT* in Auto mode. Is there a way to disable that so it actually does what I tell it to??

**alankru** · 22-11-2015,02:18 PM

I don't know about your other issues, however, your climate control should not be doing that. As soon as you adjust the fan speed manually it should take it out of auto mode and stay as set.

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**Crasher** · 22-11-2015,03:18 PM

I would recommend that the starter motor cranking speed is checked, it needs to be an almost instant 280rpm for a clean start. A failed DMF causes fine debris to get inside the starter and make it run slower. The way you do this is disconnect the head harness so the engine will not start and then go into basic settings, group 1 zone 3 (I think) and click "turbo" for a faster screen refresh. Turn the engine over and keep cranking until the lap top establishes a good connection and then see if 280rpm is achieved and maintained. The electrical fault codes caused by disconnecting the head harness need to be cleared when done.

**rowdy-999** · 22-11-2015,05:15 PM

Do these engines suffer with injector seals leaking, because the symptoms sound very much like what the 1.9s get with that issue?
If not, it could be air ingress into the fuel system somewhere.

**Crasher** · 22-11-2015,10:29 PM

Yes, they use an angle face metal to metal seal instead of a ring and this can blow by.

**Fiend** · 23-11-2015,03:10 PM

Thanks for the replies. Both the starter motor and possible leak in the fuel system have been mentioned before so I will pass that on to the garage.

**B5NUT** · 23-11-2015,03:51 PM

Something daft like a faulty temp sensor can also make it difficult to start when cold.

**Fiend** · 23-11-2015,04:02 PM

As I said, it hasn't been related to temperature so far. It was just as bad at 20'c in summer as it was in 3'c the other week. The chugging happens each time during the bad starts.

**Fiend** · 24-11-2015,12:45 PM

Originally Posted by alankru

I don't know about your other issues, however, your climate control should not be doing that. As soon as you adjust the fan speed manually it should take it out of auto mode and stay as set.

That's what I thought. Is it likely to be an electronic / programming issue that could be reset? I don't think it's the Auto button itself, as when I press that it will change to Auto mode and adjust the fan immediately.