Hi all,

I have recently purchased a dbs with about 30000 miles. It recently started to develop a miss at low rpm, when suddenly pushing down on the throttle. Prior to my ownership the car sat unused for about 9 months with very little mileage. The gas smelled stale/varnishy when removing the cap ( less than 1/2 tank was remaining) so I topped the car up fresh when I got it and put a techron dose into the tank/ drove it several hundred miles without any issues. When the fuel level dropped to 1/4 tank, it started having a low rpm high load misfire/hesitation at idle and during sudden punches (half throttle or more in higher gears, up to 2500 rpm only), runs strong otherwise above this range.

No check engine light is present, I tried to scan and see no pending codes. Next I will do a coast down procedure in case the misfire corrections are not present because nothing has been flagged according to the obd2, not even pending. If standing in the back of the car, you could feel the right tail pipe exhaust pop once every 10 -15 seconds at idle, more pronounced when loaded in gear/ac compressor engaged .

So far I have put a can of dry gas into it and filled the tank in case there is water contamination in the fuel. The problem disappeared completely for now, but I have a feeling the car may be experiencing coil breakdown?

I have owned several other db9's and vantages and have done the coil/plug job, so I have some experience on that, it feels quite similar.

Checked MAF sensors,no oil is in the intake tract or the air filter surprisingly (I am used to seeing blown pcvs and oil messes on these v12s). Also, I checked all vacuum hosing to the intake manifolds/tb area.

Approx 300 miles/one year ago, car had a service record for single cylinder misfire (dealer replaced coil/plug on that cyl ONLY). Before tearing the intakes off and replacing 12 coils/plugs/intake gaskets, looking for some input and wondering if the dbs model is sensitive to any particular fueling/plug fouling issues like the old vanquish S?

Any advice is appreciated. Thanks for your input!!

P.S does anyone have a cross referenced coil pack number for the dbs in case I decide to do this job (3 pin)?

 

Hi,
I have just read your post and your symptoms are almost identical to my 2005 DB9.
It started with a misfire at idle and hesitation on acceleration. It also has 33,000 miles on it.
I took the inlet manifolds off with the intention of checking the coils and plugs. The front plug on the right hand side had a cracked and loose ceramic insulator. Stupidly I jumped to the wrong conclusion and just replaced the spark plugs.
Put it all back together and it seemed better for a few days then the misfire was back but this time my code reader said misfire on cylinder 2.
Took engine apart again and replaced the coil on number 2 cylinder only because I read the definitive Aston Martin guide which says that it is only necessary to replace the faulty coils. Big mistake!!
Bought a second set of inlet manifold gaskets and a full set of 2 pin coils this time, I had replaced the injector "o" rings the first time, as well as throttle body "o" rings. I used these again. To help with reassembly I put a small dab of rubber grease on the "o" rings. It works a treat.
After the third time taking the inlet manifolds etc off the engine and then putting it back together the car now runs better than at any time in the 2 1/2 years I have owned it.
If you are going to do the job there are a number of posts on various Aston forums and if you have any questions just ask and I will try to help.

 

I just got my 2006 DB9 (38K miles) back from the dealer after taking it in for similar symptoms. My code reader showed no codes, and the dealer didn't find anything either.

Before taking it in I cleaned my throttle bodies -- a bit of oil on the right side, but not too bad. Cleaned the MAFs (thanks for your DIY telum01). No change to rough idle or missing under load.

The dealer found nothing wrong, but poured some injector cleaner into the gas tank. Seems slightly better, but I'll wait until it's all run through before passing judgement.

So at the end of the day just hoping the injector cleaner does its job. But I won't be surprised if I have a coil on the way out.

 

Organeer and yvr, thanks for the responses.

So today, I disconnected the battery and then did a coast down procedure properly in hopes that the misfire corrections are set now. Boy, that is fun to do on the highway. Pulled a pending p0614 code which might be a CAN error, no cel or errors are illluminated. I noticed the car said check battery disconnect and wouldn't start showing ----- in the odometer and trans gear selection when plugging my ordinary obd2 scanner into the body port, which disappeared on a subsequent restart (2011 doesnt have a battery disconnect switch).

I will keep everyone updated if the issue returns.

On a side note, on my 2006 db9, I did all 12 coils/plugs myself at 60k miles because of a similar issue and it went away. The CEL never illuminated either.... I redesigned the PCV valve system so that the valves were relocated in the front of the plenum by the radiator hosing (no longer have to remove the plenums to replace). I noticed those valves would be toast every 5000-10000 miles!

I agree do all 12 and be done! For now, car is running strong and smooth with no pops. Added the techron and dry gas in case it was a bad old tank of fuel. Still suspicious however, knowing how cruddy the motorcraft coils can be in these cars (so much heat under the hood!)

 

I'd be interested in seeing some pictures of your relocated PCV valves

 

eathonal in gas will breakdown fairly quickly and essentially creates water which will ride on top of the gas. Nowadays if you find a car with this issue, have the gas tank pumped out and use one of the products that will dry you gas, so to speak.

Also, would love to know how and where you relocated your PCV valves.

 

randyb.
Are you sure water sits on top of gasoline? I thought it was the other way round.

 

You are correct, it is what I get for not proof reading my reply.

 

Ok, so I did this on two db9's actually. I removed all the stock pcv plumbing under the plenum and ran a new alloy pipe and welded it up to Y off to the two pcv valves located as seen in the photo. This alleviated any need to remove plenums to take care of this oil issue. Should have been done this way from the factory.

I will do the same to this DBS if the oil becomes a problem, but for now I will leave it as is.

 

Does anybody have a part number for the 3 pin coil that is cross referenced? I know the factory part is 8g43-12a366-aa, which superseded the 4g43 from the early db9s. We might do the job anyways in a few months, because it bothers me that only one coil out of 12 was replaced by the dealer. I am curious to inspect the condition of the plugs and other coils. I usually buy most parts from AM like spark plugs and manifold gaskets, but anything I can cross reference is usually done like transmission pans, pcv valves etc.

Thanks.

 

Thanks! Looks tidy.

 

Thanks, it is very easy to do this when the plenums are removed, you are just relocating the pipework. I have changed pcv valves a few times on these cars, its a shame the way the oil mucks up the intakes.

 

I saw a post on here to look in PistonHead for the 3 pin cross reference.
I researched the 2 pin and the cross reference is DG-528 and as soon as the body shop patches up my car, going to put new coils and do your PCV rerouting.

Thanks again!!

 

I understand Stuart at Velocity is working on "VELOCITY" replacement coils. The last I heard they might be in testing phase? Hopefully he'll stop by this thread with an update. I spoke with a very experienced Aston tech who believes 30-35K is about the limit for the stock coils for earlier V-12's. And yes, if your tearing it down replacing all coils and plugs makes sense.

 

@AMG55, would you have more photos of your PCV relocation job?