DB9 Hesitant acceleration Missfire??

[3LDN]

I have noticed in the last couple of months the occasional hesitancy when accelerating, doesn't seem to do it from cold and there is no lumpy idle at all.
No EML light has been triggered. The car is a 2005 manual model with 15k miles, I'm thinking maybe the coil packs I imagine they are the originals.

Any suggestions would be greatly appreciated.

Many thanks

[Hutch525]

Sounds like a coil struggling under load.
When were they last changed?

[3LDN]

Many thanks for the fast reply!

I've just been through every invoice and there is no mention of the coil packs, if one is on it's way out does it not trigger the EML light? or just trigger fault codes ?

[8Tech]

I believe it will depend on the severity and frequency of the misfire detection. Irrespective of mileage, at that age it would be hugely beneficial to do both plugs and coils as well as have a good clean-up of all the intake components whilst removed.

Not the nicest job to do but not difficult, more awkward and needing a decent selection of socketry.

[LTP]

I believe the V12 logs misfires (but I could be wrong). If you haven't already it may be worth getting someone to hook it up to an AMDS or similar fault code reader to see if it tells you anything.

[JonnyCJ]

Isn't a misfire generally responsible for cat ingestion with primary cats ?

[anonymous-user]

JonnyCJ said:

Isn't a misfire generally responsible for cat ingestion with primary cats ?

Yes but with the earlier v12 cars I don’t think they had ceramic cats?

[3LDN]

Many thanks for all your replies, much appreciated.

My car was registered June '05 so did they have ceramic Cat's ?

It's booked in to Aston Martin for it's annual service next week, what shall I tell them? Given the lack of easy access in getting to the coils and plugs I guess they just change them all?

[LTP]

3LDN said:

It's booked in to Aston Martin for it's annual service next week, what shall I tell them? Given the lack of easy access in getting to the coils and plugs I guess they just change them all?

As far as I'm aware the DB9 plugs will last for ages (90k+ miles? I'm not sure), so they may not be on the service check. I'd tell them exactly what you told us and ask them if there's any DTCs (fault codes) logged that could be the the problem. What they should then do, if there's a problem that requires actions beyond normal service, is contact you with an estimate and seeking permission to go ahead with the fix. What happens next is up to you: if there is an issue and you're happy, get it fixed. if you don't like the size of the estimate you can decline the work and, knowing what they found, look for an independent near you; they may try to charge you for the diagnostic work.

What I wouldn't do is to run a V12 with a misfire, even though it's not particularly noticeable due to the number of cylinders.

[paulrog1]

I would definitely not drive the car until you either -

Get the car connected to AMDS and look at the real time misfire count, or replace the sparkplugs AND coil packs.

It's the coil packs that could be the problem, they start to break down after some years as they are deep in the car and they suffer from the heat from the engine.

Also check for oil on the airfilters, if you find oil then the PCV valves could be stuck, an ideal job to replace whilst doing the Sparkplugs and Coil packs job.

[3LDN]

Many thanks for all of your comments and advice, it's booked in to Aston Martin next week so I'll email them now reporting the fault.

[gaussianmist]

soofsayer said:

Yes but with the earlier v12 cars I don’t think they had ceramic cats?

Is this true? And if so, does that mean that we needn't worry about the engine gobbling up the primary cats on misfire?

[anonymous-user]

gaussianmist said:

soofsayer said:

Yes but with the earlier v12 cars I don’t think they had ceramic cats?

Is this true? And if so, does that mean that we needn't worry about the engine gobbling up the primary cats on misfire?

I dont know, it was a question, I think I was told that the ceramic cats were introduced during the production lifecycle by a specialist, needs checking with a pro.

[Green9]

Yes, I would also be hugely interested to know when the ceramic primary cats were introduced if they weren’t all originally fitted with them...

[3LDN]

I have read about a series one Vanquish suffering from that but not a DB9, interested in the answer too.

[Wilky7]

3LDN said:

Many thanks for all your replies, much appreciated.

My car was registered June '05 so did they have ceramic Cat's ?

It's booked in to Aston Martin for it's annual service next week, what shall I tell them? Given the lack of easy access in getting to the coils and plugs I guess they just change them all?

I've no idea whether yours has ceramic cats but my car is an 05 55 (I think my car does have them) and I was talking to Mike at Bamford Rose a couple of days ago about removing my cats as prevention is better than cure.

What I'll also say, and I know I'm in along line of people that say it, is that Mike is incredibly knowledgeable and helpful. Give him a call, he seems happy to help and advise and will give you the options for the best financial outcome to you. There's some videos on their YouTube channel talking about the subject.

[gaussianmist]

Maybe we could take a survey here and see how many others have actually experienced this (must be memorable). If the relative frequency of this occurring is quite small...….then maybe not to worry so much.