noreserve

I get the occasional rough idle in my 04 A8L when it is cold out, even after the car has warmed up plenty. Revs fall from 650 or so to around 500. That seems too low. I can feel it through the seat/steering wheel.

Dealer Service Manager says that it's going to throw a check engine light if there are any codes recorded. He said that it might be running a bit rich to compensate.

This isn't a huge issue, but I expect an A8 to idle pretty smoothly where it would never be noticeable in this fashion.

Anyone have similar experience?

Thordog61

That is funny Noreserve, I was just logging on to type a similar post. I have an 06 A8L and at stoplights I always feel a rough idle. And this is year round.
I mentioned it to my dealer when they did the 45k service but they said there was nothing wrong.
How is it that my wife's Honda Odyssey and my Lincoln LS V8 (company car) are so smooth that you can barely notice they are running, and my $85k German Sedan lopes and vibrates?
There has to be an explanation, and if so how do I get the dealer to fix it?

Mister Bally

With about 59,000 miles on the car and the fact that the previous owner did not have the 55k maintenance performed... changing the spark plugs eliminated the rough idle for me. The original plugs were quite dirty and thanks to electrode wear, the gap was greater on the old plugs than they are on the new ones.

Some plug photos are in my picture poster.

Audis or VWs 4Life

If you bring in breakfast for your service department they could likely get the plug work done in about an hour, instead of the audi quoted 2 hours. Use Bosch platinum plugs too if you plan to source them independently. Also by doing this early coilpacks are pretty sensitive to being jostled around outside there normal seating in the engine bay and ones that are on the brink of failure tend to fail right after or during the plug service. So if you do this early while you're still covered and issues crop up free coilpacks for you. I plan to do mine at the 40k service interval. You do all this work at 55k and coilpacks start to drop shortly thereafter its at the dealers discresion to cover them unless you have extended coverage.

donnie12

wow!.. i have the same issue at 73,000. i had the spark plugs changed and it helped alot but i still feel a slight idle. I am going in for a fuel injection cleaning after the holidays

noreserve

Mine seems to be only occasionally - primarily when it's pretty cold out. I've been really watching the tach the last couple of days. I notice that it normally idles around 650 and doesn't vary a whole lot up or down. I might be a little off on my original post stating it drops to around 500. I'm going to note exactly where it drops the next time it happens.

As for plugs, I'll have to check to see if mine have been replaced. I have around 43K miles.

roughyear

have u tried a bottle of fuel injector cleaner..... may help.. and an inexpensive D.I.Y application

noreserve

Correction: idles at around 625 normally it appears

CarlDude69

I even reset the throttle body via VCDS/Vag and no effect. My other other guesses are a dirty throttle body or perhaps an intake manifold leak somewhere.

At times it smooths out, but 70% of the time I can feel the idle.

mileage: 56k

MP4.2+6.0

1. Fuel injector cleaner as mentioned; I always go Techron. Two 12 oz'ers on the A8 w/ larger tank; one 20 oz. on most others.

2. Yes on plugs too.

3. Not mentioned yet; possible intake leak at a vacuum hose. I have found the cloth stuff fails starting after about 3 years. Often throws a CEL after a leak, but not 100% of the time. Don't know what year you have, but if I had a 2004 I would be doing this about now. Not a hard DIY typically.