[awk]

My 2000 DB7 Vantage may have the coil pack failing symptoms...
32k miles, sometimes stuttering in D when at rest, e.g. stop lights and stuttering under acceleration between 1K & 2K revs.
This is infrequent and disappears when warm.
Or can exist during a short journey even after warm, then park up, turn off, then leave for a few mins and restart and its gone.
If I add techron at the gas station it fixes it and just tried an octane booster (Lucas) and that also fixed it today.

If it was failed coils would'nt it always be showing these symptons?
My fuel gauge needle is sluggish to read full after fill up so could this be a dirty tank or fuel filter issue?

Experiences please would be welcome

 

[Bscoggins]

My 2000 DB7 Vantage may have the coil pack failing symptoms...
32k miles, sometimes stuttering in D when at rest, e.g. stop lights and stuttering under acceleration between 1K & 2K revs.
This is infrequent and disappears when warm.
Or can exist during a short journey even after warm, then park up, turn off, then leave for a few mins and restart and its gone.
If I add techron at the gas station it fixes it and just tried an octane booster (Lucas) and that also fixed it today.

If it was failed coils would'nt it always be showing these symptons?
My fuel gauge needle is sluggish to read full after fill up so could this be a dirty tank or fuel filter issue?

Experiences please would be welcome

Just seeing this, I partially responded to your question in my post earlier but hear is a little more detail.. Could be fuel, could be Injectors, could be bad connections, coils etc etc..

My experience was as follows: The missing never went away whether warm or cold. Changing fuel, Fuel injector cleaner etc did not help it either.. Mine is a 6 speed manual so It would miss under low rpm situations, starting out, or pulling in 3rd 4th gear low rpm situations.. once I revved the car I didnt notice any missing. I just assumed that was because with 12 cylinders and higher rpm you just couldnt tell it wasnt firing on all 12. Also, I never had a check engine light or any codes.. Engine temperature , season, day, night, short, long trip etc never changed it. Once the condition started it always missed but got continuously worse. I drove it that way for about a year but finally got frustrated and fixed it.

These v12's essentially have separate fuel delivery and ignition delivery for each side of the engine. You can easily determine which side of the engine is misfiring at idle. just advance the throttle a little at the throttle body by rotating the spring loaded throttle backwards slightly. it will increase the revs on that side of the engine only. it should rev smoothly. Remember you are just revving one side of the engine.. If it doesnt rev smoothly obviously thats the side that has the misfire. test the other side the same way and see how the engine sounds.. FYI TIP! on the v12 the driver side fuel rail feeds the passenger side intake port and vice versa. Seems obvious to some but believe me not knowing that created quite bit of frustration for me when I replaced the fuel pumps but that is another story for another day..haaaaaa

Based on my experience it seems more like a fuel issue to me. it is very inexpensive to replace fuel filters (they are located in the wheel well on the driver side). There are also micro filters in the tank swirl pot but I would not attempt that unless you are replacing the pumps which is a bear! If you can narrow it down to one side of the engine there are lots of clever ways to test your injectors and clean them. They pop out of the intake with some gentle persuasion but you will need both the upper and lower injector rubber o rings when you re-install. You can get those from Scuderia really cheap.

Changing the coil packs is expensive and time consuming but can be done with basic hand tools and lots of determination. I completed the entire project on both sides of the engine over a long weekend. It made one hell of a difference! Parts were around 3k but thats replacing gaskets , spark plugs, upper and lower o rings etc etc. and I used only correct aston martin stuff. Personally I would try the fuel related stuff before I went down that path, Just my opinion..

Hope that helps.. fell free to ping me back if necessary.. best of luck

 

[awk]

Fantastic response and feedback!! Much appreciated.
Very informative to know that once your miss started it didn't stop and mine comes and goes, suggesting fuel.
Heading out for a drive to see how its runs this morning...

 

[Bscoggins]

would be great to hear how it goes.

 

[awk]

Erratic misfires, so I pulled some codes: P0300 & P0303 - misfires and specifically cylinder 3. Looking at the Aston OBDII Diagnostic Manual these codes are to do with fuel and not specifically coils, although after following the detailed instructions in the book it could still be the coils if no fault found with fuel injectors and vacuum system. There was also a P0133 code 02 Sensor circuit slow, response bank 1 sensor 1. Looking at the manual this is a heated oxygen sensor failure, I think there are 2 on the car, but I suspect this is a by product of the misfire and not the cause.
What do you suggest, change the fuel filters still or go straight to fuel injectors?

 

[Bscoggins]

Erratic misfires, so I pulled some codes: P0300 & P0303 - misfires and specifically cylinder 3. Looking at the Aston OBDII Diagnostic Manual these codes are to do with fuel and not specifically coils, although after following the detailed instructions in the book it could still be the coils if no fault found with fuel injectors and vacuum system. There was also a P0133 code 02 Sensor circuit slow, response bank 1 sensor 1. Looking at the manual this is a heated oxygen sensor failure, I think there are 2 on the car, but I suspect this is a by product of the misfire and not the cause.
What do you suggest, change the fuel filters still or go straight to fuel injectors?

You are correct, it could still be a coil! And I would tend to agree the p0133 is due to the misfire possibly from fuel not being burned completely. If it was filter related I would think you would have misfires on all cylinders and not just #3. I would think starting at #3 injector would be the least invasive place to start. I would double check the connection at the wiring loom on the injector. The clips are known to become brittle . In fact a couple of mine were broken when I did the coils. I use an old school technique when looking for vacuum leaks and there are quite a few vacuum connections and tubing in the throttle body area. Just get a piece of thin hose and hold one end up to your ear like a stethoscope then move the other end around the vacuum connections with the car running. The sound will increase dramatically in the area where a leak is occurring.

if you pop the injector out there is a cool way to clean it with a 9 volt battery and some carb cleaner I found on YouTube, you can hear it click also to make sure it’s functioning when you apply the battery power.

hope this helps! Good luck

 

[awk]

Having ordered the O rings, the plastic gizmo that sits on a can of carb cleaner that you insert the injector into for cleaning and learning the 9v cleaning trick - I put another dose of Techron in the tank whilst waiting for things to arrive and low and behold I made a 15 mile trip with no misfires. This misfire free joy continued for 3 days and then the odd little miss came back randomly.
Today I removed all of the injectors, cleaned them, replaced the o rings which were tired and then re assembled. One of the fuel rail bolts nearest the firewall would not seat and I was paranoid about cross threading so left it half way and turned on the ignition and no leaks and went for a drive - DO NOT EVER DO THIS!!!
Fuel smell was really bad and #2 injector was leaking from the top - I presume having not secured the end of the rail properly the pressure just lifted the rail.
Turned all of, released the fuel pressure in the rail then removed the bolt and swapped it with the middle one, both seated well and I made sure the rail was level and seated securely into all injectors on both sides, then torqued the bolts.
No leaks, no miss but now a strong fuel smell.
I am embarrassed about my lack of attention on the bolt, and posted it here to inform.
The main output though is misfires can also be attributed to fuel injectors and if you see improvement after a couple of doses of Techron then its well worth the effort to pull each one and clean it. Dont forget new top and bottom O rings -mine came from Scuderia Parts.
Big thank you to Bscoggins for his thread, responses and advice. I would not have tackled the job if it was not for his posts!!