PJH

I have noticed that every time I start my a6 2.7t (550 miles/ 3 weeks old) when it has been sitting overnight I get a rough idle as the rpms begin to drop to around 1200. It starts fine and goes in fast idle, but as the rpms begin to drop the engine starts to shake and for a brief second it cuts out - like I had turned the key off for a split second. The idle then continues to drop as it should but not that smoothly. This only occurs on the initial cold start. There are not any problems on a hot start or during driving. Idle is smooth at all other times. Any ideas?

Capt Ron

For what it is worth, my 2.7T (3200 miles) does the same thing.

The problem started about the same time "summer formula" gasoline was introduced in my area, around the first of April.

My guess is the car doesn't like a high Ethanol food at breakfast.

2.7tDallas

even when it is not.

My rough idle stopped when they replaced mine

PJH

Come to think of it, I don't recall this symptom until I filled up with Shell premium a couple of days ago. Did you have this investigated by Audi service? The car runs beautifully after this cold start and never reappears during driving. I'll try another brand of gas at next fill up. Unless this symptom becomes more pronounced I'll live with it as I don't cherish leaving the vehicle overnight at the Audi dealer so they can tell me it does not happen.

PJH

Was the rough idle constant or as I described? Would you happen to know the part number that was replaced?

Shine.S

I have the same problem and my dealer's service department doesn't have a clue. They claim to have checked the temp sensor and it was okay. Let me know if anyone finds a cure.

Shine8

April

Sometimes the O2 sensor sends the wrong signal or the ECU has a glitch reading it.

2.7tDallas

Mine was the opposite, started great, rough when hot. April is right though

KazooAudi

Have had the same problem, as have many others. There is a "fix" from AoA, though I have not seen a TSB on it. It requires an ECU re-program - what your dealer will tell you (if they can find the info on it) is to leave the car for a few days, they will send in your ECM for re-programming and then put it back in when it returns. (Don't know exactly what is being re-programmed). I refused to do it their way, and made them send a re-programmed ECM to the delaer, who then swapped it (15 minutes instead of several days.). Haven't had the problem since, but then for me, the problem was verrry dependent on ambient temperature, most noticable at lower temps, which we hopefully won't have for several months!