Hey guys,

I need some urgent help. I just got my 2005 AM DB9 serviced at this independent shop (due to the emissions and engine light going on), and the following service was done:
Oil change
oil filters
air filters
spark plugs
the mechanic inspected the ignition coils, and said only 1 of them needs replacement, the other ones are in very good condition, so we only replaced one of them.

When I went to pick up the car, the mechanic said it still has a couple of misfires, and there was a rattling sound coming from the exhaust. He referred me to another guy that replaces the cats. I took it to the other guy, he replaced the cats, and the rattling is gone.

The car still has misfires though and shakes when accelerating, and turns off when pushing the gas to hard. Im taking it back to the first shop, they said it must be the ignition coils, which they're going to replace for me.

I bought this code reader, and i was wondering if you guys can give me some input if those are pointing at the ignition coils, or at something else. Here's the (long) list:

Stored Codes:
P0606 - Control Module Processor
P2105 - Throttle Actuator Control System
P1797 - Unknown Diagnostic Trouble Code
P2106 - Throttle Actuator Control System - Forced Limited Power

Pending Codes:
P0606 - Control Module Processor
P0705 - Transmission Range Sensor "A" Circuit (PRNDL Input)
P1797 - Unknown Diagnostic Trouble Code
P2105 - Throttle Actuator Control System - Forced Engine Shutdown
P2106 - Throttle Actuator Control System - Forced Limited Power
P0306 - Cylinder 6 Misfire Detected
P0316 - Engine Misfire Detected on Startup (First 1000 Revolutions)
P0606 - Control Module Processor
P2105 - Throttle Actuator Control System - Forced Engine Shutdown
P2106 - Throttle Actuator Control System - Forced Limited Power

Permanent Codes:
No permanent codes found.

Before these codes i had cleared the codes accidentally but i remember they listed some misfires in several cylinders. The shop that replaced my cats said they got the following codes: P0304, P0306, P0307, P0309, P0310 ...which are all misfires in different cylinders. Those must be the ones i had cleared.

Does this hint to ignition coils must be replaced only, or do the codes mean there is a bigger issue behind the coils?

Please heeeelp =(

 

An 05 car probably needs spark plugs and ignition coils. It's a big job as the inlet manifolds have to come off to get access, necessitating new gaskets etc. Over a period of time the misfiring probably fried you cats with unburnt fuel.

A proper service with a good competent person who understands these cars should sort it out.

It might also be prudent to change the oil separator valves that you can get access to when the manifolds are off.

 

would start by replacing all coils and plugs and then have the main dealer doing a misfire correction with the AMDS.

See this tread ; https://www.6speedonline.com/forums/...ion-coils.html

 

First rule with diagnostics is check all the simple stuff first.

The first thing I would check is to make sure that the primary O2 sensors are connected the correct way round, and that they haven't been reversed. I don't mean primary & secondary reversed, I mean the primaries plugged into the incorrect primary. If someone was replacing catalysts in your manifolds they most certainly would have disconnected them, and may have re-connected them the wrong way round.

Another important question - were these problems present BEFORE you went in for this service or only came up after? That will help narrow down a lot.

If they were present before, are still present and the mechanic is correct about the coils being in good shape, then you might have a bigger problem.

I don't want to scare you unnecessarily, but one of the potential problems with these V12's, is that a prolonged misfire or incorrect running condition can cause catalyst failure (which you have alluded to.) Due to the proximity to the cylinder head and the firing order etc., the potential exists for pieces of broken down catalyst to be aspired back into the combustion chamber, which has the potential to damage valves, valve seats and combustion chamber walls.

Most likely this is not the case, but I would definitely like to know - was the car running reasonably well, but not terribly when you took it in, and now is terrible? Or was running like this before and the condition persists?

 

Hey, thanks for spending the time to help me on this. When i took in my car for service both the engine light and the emission service light were on. it took me about 4 weeks to take the car to service, but i only drive it like once a week (its my weekend car). So i heard the misfiring and idling , and i got concerned so i took the car into the shop for diagnosis. It got worse while it was in the shop.

Also in case this info helps: my DB9 has 26k miles. I bought it with 18k miles and added these miles within 6months (used it as my daily driver till recently). I called up the previous owner to find out about the previous service, and he said he didn't take it in for service as he only drove it for 6 months. I couldn't get a hold of the owner before him, but the car may not have been serviced for a while. Can that have contributed to the issue? I mean the car still only has 26k miles.

 

I've got 26K miles on my '06 and it runs really well. I bought it with 11K miles and the previous owner hadn't serviced in 18 months (probably due to low annual mileage). I serviced it at the local dealer as soon as I got it (no issues) and have kept to the annual service regime since.

Why not take it into the dealer? They've got the proper diagnostic gear.

 

Yes i was thinking of doing that next. I ordered the ignition coils already and this shop is going to put those in for me for free, so I'm doing this first and see if this is going to resolve the issue or at least part of it.

If the fault codes were pointing at something else i would ask the shop to check those too since they're taking the manifolds off.

If the issue is still there ill take it to the dealer. The ignition coils should be delivered on thurs/fr and installed same day. Im just hoping that'll take care of everything

 

If it were me, I would get them to do a compression test while they have the coils out. It is very simple and relatively quick to do one.

 

Good idea, they might've already done that when they said the coils are good but I don't know. I'll let the shop know in case they haven't, thanks for your input

 

How can the shop tell you only 1 coil needed to be replaced along with all the spark plug(they had misfire DTC's on both banks), they would have to use a scope with a damn high resistance to not blow the leads and or scope to test a coil's secondary windings..sorry just doesn't add up. In the codes they had was P0306 and yet your still having this issue with a misfire on cyl 6...I would really start to wonder about the experience and reputability of this garage..

On these early V12's I always include all 12 coils when I am doing plugs due to a misfire..I have gotten burnt so many times in the past..1 coil is faulty so you replace it along with the plugs on that bank, can still feel a slight stumble but not flagging anything in realtime misfire monitoring..under a year later car returns with a misfire on the same bank but a different coil..nonetheless your paying me to rip it apart again, would of been cheaper to just rpalce everything on the first repair...so all 12 plugs and coils I replace unless its a warranty case and they only authorize the suspected parts, but it's on warranty's dime not the clients so let them pay..

On your DB9, if they really did replace the plugs and the 1 coil like they said..either there are other coils faulty once they are hot....or the garage broke the coil connectors and thought sliding them in place with silicone would keep things together.......just it didn't and now the coils need to be accessed again..

Do you mind me asking how many hours they charged you to replace the spark plugs?

 

So these codes were read after that service was done. Regarding the hours they charge $125/hr which i thought was reasonable. I called the AM dealer to just ask how long this service would take them, and they quoted about 6-7 hours. My shop quoted me $750 flatrate. They ended up spending a few more hours, and now that im taking the car back in they will take the manifolds off and spend another 6 hours to replace the coils without charging me again. So i think the shop was petty fair with the labor?

Do you think there is a chance only the coils may be bad, and the all those codes come up as a result? im not familiar with how these codes work.

 

It's good they are taking this upon themselves to solve the concern, on there dollar..I hear stories like this and the garage leaves the client to solve it her/himself even after they were paid to fix the concern that was not solved...

The time is with in reason, I've seen places charge north of 15hrs at $120-200/hr..but the 6-8 hour mark is a good quote for plugs providing nothing else is required to check(leak down, compression ..etc).

For V12, when the car is over 4 years old, and I have a misfire confirmed on more than 1 cyl..I change all coil and all plugs. The coil connectors due get weak and crack when touched, so I have these connectors in stock "just-incase", if 1 breaks I don't even try to fix it, I just replace the connector with a new one, better safe than sorry. I see a large amount of misfires from another place that used silicone to hold the broken connector in place, connector backs out and forces a misfire of that coil..sucks for the clients that drive low mileage and a misfire happens like such after a year from the previous repair, pay an indie garage $800 to fix, then a year later another $800-1000 to repair a broken connector..I'm not stating this is the situation, just what I've seen on my end.

Not sure if you told us, is your car auto or manual?

 

Mine is auto. Do you recommend replacing the connectors as well? or do they come with the new coils?

 

"What ain't broke don't fix"..the connectors do not come with the coils, if the connectors are not broken then there is no reason to replace them..really just money wasted unless cracked/damaged/loose. But I would highly recomment replacing all coils and plugs versus just the ones that recorded a DTC..

 

Oh now i see what you're saying. correct me if im mistaken, but the fact that the coils snap in does that not mean that the connectors are not broken? Ill point this out to the mechanic to check if they do, but i think this time they will have a thorough look at every detail anyways.