jhandy1

Ok,

here are the details-
2006 S65 75000 miles
drives fine. sometimes start up is hard after driving- a little rough and sputters. turn off and on and starts fine.
Under acceleration- around 4500 rpm the car misfires and CEL turns on.

codes read
multiple misfire
misfire 11
misfire 12

if i drive it normal- no issues.
all scheduled maintenance was done at Dealer in Texas.

So... I do not want to start replacing expensive parts- I am thinking Coil pack- but what side?
should I do the plugs as well? Voltage regulator?
that's a lot of cash already- change both coil packs if already replacing one?

what is a good spark plug?

Some direction please.
Thanks,
James

amstel78

Hey James,

Cylinders 11 and 12 are driver side. If you're standing looking at the engine, cylinders 1-6 are passenger with 6 being closest to the firewall. 7 and 12 are on the driver's side with 12 being closest to the firewall.

I would suggest changing plugs first. As your car already has 75k on the clock, do you know if the plugs were changed out at the recommended 60k interval? If not, pull the plugs from 11 and 12 and take a look. They should be slightly brown without any oil fouling or broken center electrode. If they look fine, this is what I would do: pull the plugs from 11 and 12 and swap them with cylinders 7 and 8. Put the coil pack back, clear the codes, and test drive the car. If the CEL comes back with fault codes P0311 and P0312 after the plug swap, then it's probably safe to say the coil is bad. If on the other hand, the CEL comes back with codes P0307 and P0308 indicating a misfire in cylinders 7 and 8, then chances are it's the plugs.

The above is exactly the process I'm going to follow tomorrow as like you, I have misfires in cylinders 5 and 6 on my 2006 S65 with 55k miles.

As for plugs, the recommended replacement is an Iridium plug, specifically NGK IFR6Q-G ( manufacturer part #5648).

If you determine that it's the coil pack, before replacing it altogether, have a look at the rubber plug insulators. If they're cracked, dry, and brittle, they can sometimes be the cause of a misfire. If they look OK, then it really most likely is the coil pack. You could get a rebuilt one for $700 from Clark over at www.v12icpack.com. Those feature a 1 year, unlimited mile warranty. Otherwise, you can get a new one from a dealer for $1400 or some online vendors from anywhere ranging from $900-1200.

Good luck and let us know what happens.

Edit: to address the rest of your questions, if only one bank is misfiring on 1 or 2 cylinders, the voltage regulator is unlikely to be the culprit. If all cylinders are misfiring on one or both banks, then the voltage regulator can't be ruled out.

If you have to replace the coil pack on the driver's side, I wouldn't mess with the passenger side unnecessarily. There's always a chance that removing and reinstalling the coil pack could damage something in the process and will end up causing you more heartache and a lighter wallet. On the other hand, if the plugs are still factory, I would really consider replacing all 24 plugs while you have the engine apart.

shardul

iTrader: (1)

change the coil packs don't even waste time on plugs it wont solve the problem.

amstel78

Unless you pull the plugs and check their condition, how would you know? There are many causes for a misfire, and damaged or oil fouled plugs can cause them. And if it were bad plugs, replacing the coil with a new one won't solve the issue and can end up damaging the replacement coil pack in the process.

jhandy1

As far as I can see in paperwork- the plugs are original.
My dealer- I guess in hopes that I will start using them- offered a free diagnostic appointment. They claim to be able to tell me if it is the plugs or the coil.
I will go tomorrow and let them play with it and see what they say.
I can do it myself- not worried about that- just hate burning money for no reason.
If I take the coil off- I suppose I will do the plugs.
Ill post the results of the free testing.

jhandy1

So....
The service department came back with the CHARGE AIR COOLER PUMP failure.
do they mean the intercooler pump?
is that a DIY thing? I thought bleeding the fluid is really difficult
they say that this is the cause of the misfire because hot air is being sucked in.

Does this sound right?

also transmission mount needs replacing.

amstel78

That would be the intercooler water pump. Doesn't sound right to me. If the pump fails, you don't cool the forced air very well and the car loses power. But I don't expect it to be the source of a misfire in only 2 cylinders.

jhandy1

Yea- that is what i said. they want 1000 to change it out. They can not guarantee that will solve the issue.
but that is what the experts say is the cause of the multiple misfires.

cmpcpro

Run away from that place! The pump is 100- something dollars and super easy to install. Doesn't need to be bled if your just changing the pump it will bleed itself

ItalianJoe1

I have this similar issue. I did plugs and ended up doing one coil as it broke during removal. Still has a hot misfire on re-start. I want to change the transformer next as soon as the budget recovers. Even with all new plugs and one new coil, I get scattered misfires on both banks when it has the hard starting.

To the guys saying pull and inspect/swap plugs, don't waste your time. If you're that far in, just install new plugs. The new coils are an updated part with improvements, if you want the car to run perfect it's a necessary investment unfortunately. The coil is around $900/ea, the plugs are $9/ea. So for just over 2K plus labor, you can do new everything. Not really that bad on an engine of this nature.

amstel78

I decided to go that route. Have 24 brand new NGK IFR6Q-G plugs sitting in a box on my floor. What I will do though is just replace the passenger side plugs first since my only misfire is in cylinders 5 and 6. I don't want to mess with the driver side until I reach 60k on the clock or until the driver side coil pack goes south too... whatever comes first.

BTW, where are you finding plugs for 9 bucks a pop? I bought 24 at $250 shipped which is the lowest I was able to find, making each plug a little under $10.50 per.

ItalianJoe1

It might have been closer to 10, they were 9-something each bought from my dealership at employee cost, which for me was about the same as buying online but I didn't have to wait or deal with shipping and such. They were in stock already. I bought other things at the same time but I believe it was $220-230 for just the plugs including tax.

amstel78

Well, wherever you got them from, that was a great price.

Just worried after replacing the plugs on the passenger side that more misfires in other cylinders might appear. This was something Clark from v12icpack.com mentioned to me in passing. That said, I'll order a rebuilt pack from him and if things don't work out, at least I'll have a replacement ready to go.

jhandy1

OK- I changed the inter-cooler pump. And against all that I thought- perhaps the Dealer mechanic was correct- because i drove it like a rented mule and the temp stayed down and the car did not misfire.

So for now- if you have a misfire when hot and under load- think the inter-cooler pump.
BTW the dealer wanted 1000$ to change it, I did it in 30 mins and used only a jack stand.
way super easy.

amstel78

Glad to hear your intercooler problem solved the issue although I still think it's strange that it was the culprit.

Did you source an OEM pump and if so, what was the cost and price?

jhandy1

https://www.fcpeuro.com/ cost was 110$ and 9$ for some hose pliers.

cmpcpro

I bought the updated Bosch pump from BMA auto parts.. make sure you get the updated one.. if memory serves its around $140 or so.

E42AMG???

Updated pump part number ends in 010 depending on where you buy can be had for 105-150 dollars.

E42AMG???

Also the cm30 pump has worse flow and costs more then the Bosch 010, even though you see threads where people upgrade to it.