If you own a V12 Aston Martin like the DB9, V12 Vantage, DBS or Virage, you’ve likely heard about the common issue with lumpy idle that is attributed to a misfire condition involving the spark plugs and coil packs. I’ve done an extensive series on determining the issue and how to replace them (check it out here). Getting your parts together for that project has one complication – are the coil packs the original 2 wire or the updated 3 wire design? Even contacting Aston Martin won’t resolve the question – they don’t know. They will tell you they slip streamed the change sometime during production in 2006 ‘ish. The only way to tell for sure it to be halfway through the project when you can finally see the tops of the coil packs and count the actual wires. This is of course a tough time to stop and order the correct coil packs, leaving your car disassembled for weeks waiting on parts. If you just play the odds and guess, you may end up with a dozen incorrect (and expensive) coil packs. This misfortune has definitely happened to a few owners. Let me show you how you can find out for sure BEFORE starting the project.
Credit for this tip goes to Mike at Bamford Rose in the UK. I was chatting with him about this challenge, and he suggested that you can in fact do some inspection in advance and know for sure. So I thought I would give it a shot and share it with you.
Have a look at this photo I took of my car when I was changing the plugs and coil packs. This is the primary bank of cylinders, the right hand side of the car, officially cylinders 1 through 6.
In the photo you can see the two wires coming off the front of the connector on the cylinder #1 coil pack. There is a green/blue (mostly green with blue stripe) wire and a brown/yellow wire. So, for my car you can definitively tell I have a 2 pin (2 wire) coil pack.
For some reason I am yet to learn [please comment below if you know definitively], Aston changed the design from a 2 wire (pin) to a 3 wire coil pack sometime during production in 2006. I do know the additional wire is a BLACK ground wire. The six ground wires per bank collect together in the wiring harness and the ground supposedly bolts to a spot on the back of the cylinder head (that we can’t see easily). Here is a snip of the wiring diagram that shows the official original 2-wire and upgraded 3-wire wiring diagrams.
Unfortunately it’s not as simple as removing the spark cover and taking a peek. To take that cover off (as in the photo above) I had to do a MAJOR amount of work that includes removing the glorious aluminum intake manifolds on the top of the engine. Honestly, once you are at the step where the spark plug covers are off, you are nearly done.
Mike’s tip was to remove the front two screws in the spark plug cover and gently pry it up (without permanently bending it) to peek inside. Let me show you how.
You don’t need many tools:
- T20 Torx bit
- It is easier if you have a 1/4″ drive version since the PVC breather pipe is right over the screws that need removed. Can probably be done with 3/8″ drive if you are careful.
- Ratchet and a 6″ extension to make life easier
- Automotive non marring interior pry tools
- I got a set from Amazon for about $13 USD here but you can usually source them at most any auto parts/tools store.
- Good, bright inspection light (essential)
- My favorite is this little gem available for about $11 USD from Amazon. It’s very bright (150 lumens), and if you are looking locally the magic here is its a COB LED light.
This process takes only about 5-10 minutes.
- Tip – do this when the engine is cool. I did it just after driving and these parts are very hot to touch.
- Remove the two front and visible T20 torx screws on the spark plug cover plate.
- For the upper one you might need to gently push the PCV breather pipe rearward to get clear access to the screw.
- For the lower one use your 6″ extension
- For both of them be VERY CAREFUL to not drop the screws. Seriously – if you drop it, it disappears into the void below and you’ll be doing a load more work to find it. Just slow down on the last few threads and use your fingers to unscrew it keeping a grip on them.
- Work your smallest stiff non-marring plastic pry tool in the front edge between the spark plug cover and the valve cover. Just ease it in to get a small gap started.
- With the slight gap opened by the first tool, slip a thicker, stronger/larger tool in along the central edge closest to the intake runner. I used more force to work it in until I felt I was pushing my luck on bending it, and I had opened about a 1/4″ gap at the front top corner (see pic below).
- With the gap open, I positioned my inspection light so it would project light into the gap from the side at the front (see picture)
- Now the tricky part – peer into the lighted gap and find an angle where you can just barely see the electrical connector to coil pack #1, and count the wires. Are there 2 or 3? If you can see a solid black wire its likely a 3-pin coil pack.
- You’ll be looking at it from the side, so it may not be easy to see all the wires. You could always have something like a long wood cooking skewer handy to gently tease the wires to improve the view to count them.
- Keep in mind you might need to get your head into a odd position to see into the gap, and/or use a mirror or something to get just the right angle.
- After you’ve seen what you needed, just button things back up:
- Remove the pry tool and the cover should sit back flat like it was originally.
- Install the two screws starting them by hand at first and being careful not to drop them into the abyss.
- Snug the two screws with the T20 torx and the ratchet. Don’t overtighten, just snug is fine. You don’t want to strip the soft aluminum threads in the valve cover with the harder steel threads of the screws.
That’s it. Now you can head back over to my article on the parts for replacing your coil packs and purchase the correct coil packs for your car!
Here is a short video showing you how to tackle this.