Db9 lumpy idle

[schmarnst]

Hi all,
Can anyone advise me, I have an 04 Db9 auto with less than 30k on the clock, and recently when the car is in drive (or reverse for that matter) on tickover, the car wobbles as if something is off balance.
This doesn't happen when the car is in Park or neutral, or when under acceleration but is definitely noticeable when for instance stopped in traffic or moving slowly without accelerating.

Has anybody else had a similar issue or can suggest what might be the possible cause? I never noticed it a while ago, but it's getting on my nerves now!

Any suggestions would be appreciated, as I haven't got a clue where to start and I am reluctant to send her to a dealer due to price.
Thanks in advance!

[pschlute]

My 2005 DB9 did the same at about 35,000 miles, although the lumpy idle was noticeable in N also. It was a failed coil.

Another symptom on mine was under hard acceleration the emissions warning light would come on.

[schmarnst]

I can only think it's something to do with the gearbox, as everything works fine, with no warnings coming on, even when plugged into diagnostics...

[dbfarmer]

I have a 05db9 and had exactly the same problem. New set of coils and a new set of plugs and totally sorted. Made a huge difference. It was done at 37000 mls.

[schmarnst]

Any issues under acceleration? Or just at idle in gear?
It's just had a set of iridium plugs, and it hasn't made any difference.

[dbfarmer]

Seem to remember acceleration was not so bad but it was worst when idling in gear. Have you fitted new coils ? It is recommended to change them at 35000 mls and that was exactly when mine went. Been going like a dream since.

[paulrog1]

What sometimes happens when the sparkplugs are replaced there seems to be a risk that a coil (or coils) fails.

I've read that over time the engine "cooks" them so the first time they are interfered with they are prone to fail.

I would replace all 12 coils, clean out the two throttle bodies and the car will run smooth.

[schmarnst]

Ok thanks, might be worth a try. Can anyone recommend where to get them from?
The prices I've seen vary from mid 50s to high 60s each.

[schmarnst]

Also, if a coil pack/s failed, would the dash not light up like a Christmas tree? Or at least something would come up on diagnostic tests?

[paulrog1]

I know getting them from Aston Martin can be pricey, you will have to remove the inlet manifold also, you may also need to replace the gaskets.

Look at this - http://www.pistonheads.com/gassing/topic.asp?t=110...

You should confirm what type you have as some are 2-pin or 3-pin.