I've had this problem ever since having my 54 plate B6 Audi 1.9 TDi AVF 130bhp PD A4 Avant.
It's always been a poor runner for the first 5-10seconds of a COLD start. Never does the issue occur after a warm start or even if the car was used say in the morning and you use it in the afternoon. It's ALWAYS when left overnight.
Car Starts fine, no problem cranking etc....but once fired it runs very rough idle and quite noisy for about 5-10secs.
If you rev the car, it sounds quite noisy (i almost would call it "tapety") and if you pull away sometimes it very easily stalls.
The car ALWAYS with these rough starts, chucks out copious amounts of black smoke (which even this morning I thought looked a tiny bit blue - if that makes any difference)
This only happens at rough starts, don't get any black smoke on warm starts and no black smoke even when booting it or running it normally. It's a very un smokey TDI otherwise.
What I have done so far:
1. Replace glow plugs with bosch ones (this helped with a poor crank in the cold weather)
2. Had a full service, air filter, pollen filter, fuel filter and oil filter and oil change
3. Had the alternator pulley changed as this was knacered
4. Had the Coolant Temp Sender changed as knacered
5. Put injector cleaner through the car once (the good stuff)
6. Had the EGR valve and manifold cleaned (not that dirty anyway) but cleaned nonetheless.
7. Battery has been checked, running about 75% and recommendation this probably should be changed (get the brake warning light sometimes in the cold which is related to poor battery)
8. Had the electronic engine mount changed as this was throwing an error
9. VAG com shows NO errors at all.
So what other things could be a problem?
Battery for sure could be a cause
Possibly the injector loom but my understanding is this would throw up on VAG com (havn't had it checked as such physically)
Mechanic thinks the DMF could be showing signs of going, but not sure this could cause rough starts
Any help on this really appreciated....I really can't get to the bottom of it.
I have done an awful lot to try and diagnose but don't seem to be any better off. The things above have helped, it's not quite as bad as it use to be but still obvious.
It also seems to be worse in cold weather but it isn't always the case.
It's almost like a fuel starvation issue......
Cheers for reading!