I have 99 A6 2.8 for few years i was really happy with the car until recently. In the morning the car starts and runs great, but if i try to turn the car on later in the day and the engine is worm it takes about 20-30 seconds before the engine starts. If the car is warm the acceleration is bad it seems like the car is very slow.
I recently changed fuel filter, air filter, spark plugs, and head cover gasket (because of oil on spark plugs).
If anybody has any idea on how to fix this please help.
Thanks

 

Check your fuel pressure (or pay to have to checked). An "on the verge of dying" fuel pump will act something like this.

Also, read your codes and check your coolant temperature sensor readings *** it may be faulty.

Bob

 

Also look at MAF sensor and the CTS (coolant temp sensor).

 

i have a 2.8 also .. i thought they were all slow on acceleration

 

Car run and drive OK in the morning until reach working temp. Temp gage showing ok temp (right in the middle). From that point car accelerate very slow and takes long time to start again.
Thanks for advice. I will check fuel pump pressure and sensors and let you now results....Thanks for help.