deml0

seems to happen after the car has been parked for some time, for example, overnight or ~6 hours. also seem to coincide with colder temperature (that's just speculation, but i don't recall this happening over the summer). so immediately after the car is started up, the rpm oscillates between ~1000 and ~2500, and the engine sounds horribly rough. it initially drives with some hesitation.

yet, when warmed up, all is ok. starting it up again, the rpm is under 1000. smooth sounding engine. no hesitation.

what gives? o2 sensors (they seems fine)? spark plugs (replaced 2 years/37k miles ago)? coil packs? please help. thanks.

Always Overcharged

talks about fuel pressure regulator when the symptom of rough idle when cold is entered.
Maybey you have a blockage in the return line.
Try loosening the fuel cap at next cold start to see if reduced vacum improves the issue

deml0

i wish, 0 codes from vag

RapidA8

I own a 2000 A8L and I had the same problem!!! I changed the spark plugs, checked the ignition coils, spent $500.00 at the Audi dealer to clean the throttle body and set it to specs (this was their idea!). Anyway I had to take the car back since the situation did not improve. After 1 week I finally got my car back and it is back to normal!!! It was the air meter (mass airflow sensor)! They charged me $282.00 for labor and $138.68 for the sensor. Anyway you can buy one for much cheaper and install it yourself. It's your lucky day! I wish I knew...

deml0

i'll check the maf, but checking my records, i had that replaced at 64k (got 109k now) in august 2004 at the dealer. they found the vac lines were broken and the maf "out of factory spec". they replaced the vac lines and maf. they also cleaned the throttle body. i suppose the maf could've broke again. i'll check. thanks. good info!

Always Overcharged

past it and as a result dust can build up.
A simple log of the maf sensor in measuring blocks will show if it is in spec.
If not try cleaning the wire [carefully]

RapidA8

It is just weird how my car behaved the same way. When you first turned the key it almost sounded as if the engine had no oil inside!! And then it will accelerate chaotically. Sometimes it would stall and I had to start it again... depending on the temperture outside. It ran perfect after that... once warm it was back to normal... let it sit more than 3,4 hours and it would start rough, not as bad as the first time in the morning though.

deml0

well said, those are my symptoms also!

deml0

i'll definately check that out, thanks!

deml0

loosening the fuel cap is easy enough to do. i also plan on pouring some techron into the tank. thanks.