leodangelo

Saturday I was out running errands in my 2005 CL65. For the record it has 74k on the clock. Anyway, I went to start the car and it stared and then quickly died. I tried a few times and the same thing happened. Eventually it started and was obviously misfiring, CEL came on and it appeared to be in 'limp mode'. I should note that about a year ago I was driving and my car literally shutoff while I was going ~40MPH. When I tried restarting it did the exact same thing (fired up and died right away). It eventually restarted and has not happened since.

I got it home and put the scanner on it and I got:

P0309
P0303
P0302
P0307
P0300

After letting it sit over night I went out and it fired right up... Does not appear to be misfiring anymore.

I've read all I can on misfire issues and have determined it could be any one of:

Coils
Transformer
Bad CATS
Fuel Pressure Sensor
Fuel Pump
Plugs
CPS
Bad Fuel

Because I got misfires on both odd and even I'm leaning towards the transformer, CPS or Fuel Delivery. I don't want to spend the $$$ to start swapping parts so I was wondering if anyone had any 'testing' ideas to determine the best course of action?

Thanks in advance.

shardul

iTrader: (1)

start off with checking fuel pressure of the rail. should be about 70 to 80 psi at idle.

leodangelo

Thanks Shardul,

I appreciate the advice. I was thinking I would start with fuel pressure as well as it's easy to check. I actually suspect that one or both of my cats are clogged... When I get on the gas hard I smell a strong sulfur smell as soon as the fun is over... Any way to test the cat's on my own or will I have to take it to the dealer or indy to have them tested. Thoughts?

Thanks in advance!

MooJohn

You'll test and diagnose forever, only to discover it's either a coil pack or the ignition transformer. Unfortunately there isn't a way (that I could find) to tell which is bad without having a spare transformer on hand to swap in place. That's a 5 minute job and a ~ $750 part. Odds are about even as to which is the culprit.

The ignition coils can be found at Advance Auto Parts for half the cost of OEM, but you'll want to do the labor yourself or have a specialty shop do it since the dealership typically won't touch parts they didn't sell.

I couldn't find a single forum post where someone had a v12 misfire caused by something other than the coil packs or transformer.

Edit:

I should add that since you have misfires on both banks, more troubleshooting is warranted. 99% of the time all the misfires are on one side which makes it a far easier diagnosis.

leodangelo

Thanks for the Reply,

I agree if it was one bank I would be 99% sure it is a coil pack. Being that they are on both it makes me think other wise. I have read quite a few posts regarding misfires that were actually fuel delivery issues and a couple related to bad cat's. Both of which can cause misfires on both banks... I'm not an expert here but I certainly don't want to take my check book on a fact finding mission especially since I just replaced the motor mounts, ABC accumulators, IC pump and had a service to the tune of 4600.00.

I've decided I'm going to work on the car myself from now on as I don't really like the results for the amount of money I spent. I feel pretty confident I can handle most everything we talked about (including the above mentioned repairs). I wanted it fixed fast so I decided to pay... Silly me... Should have just done it myself and saved the $$$ It took a week anyway.

Again, thanks. I will be sure to post what I find as someone is likely to follow in my foot steps at some point.

principledchiro

Leaning to fuel pump...due to both cylinder banks. Fuel pumps show there weakness well into engine running then as resistance increases they heat up thus slow down. Your last run left low fuel pressure upon shut off...this condition existed on cold start causing misfires. But who knows..?

leodangelo

Thought I would follow up on this in case it helps someone in the future.

After taking my car to the dealer they tracked down the issue (not confirmed as it is still at the dealer). They are saying it was caused by the fuel boiling in the fuel rails. Apparently there is a software update to deal with changing fuel between summer and winter.

Ultimately this issue was also caused by an independent mechanic. I had them replace my intercooler pump and they did not properly bleed the intercooler circuit.

Does this make sense to anyone else? My IC pump was dead and I did not have this issue...

-LeoD

shardul

iTrader: (1)

well the intercoolers sit on what on top of the fuel rail so if they were full of air and not water i can see how the heat transfer will alter the temperature of the fuel.

Crissus

Ehh What? Software Update to deal with summer/winter fuel??? On a 65 AMG? Mercedes builds cars that drive everywhere under every condition. How to solve air bubbles in the FUEL line with a software update?
Does your AC work? Normally if that fuel Rail has a return line to the tank, Mercedes cars use a fuel cooler thats connected to the AC on on side, and to the return fuel line on the other side, to avoid that issue. It can also be related to the fuel fumes recirculation stuff with that charcoal filter.

A dead or wrong bleed IC pump should not cause misfires.

leodangelo

A/C works fine. It sounds fishy to me too... I can put my hand on the intercooler (while it is misfiring) and it is warm but not hot. The issue is definitely heat related though. If I open my hood and let it cool for ~10 minutes it fires right up and runs normal until my coolant temp rises to 95 degrees. The software update is a lot cheaper than a coil or transformer replacement but I don't think it will 'fix' the issue.

-LeoD

biker349

i go for ignition module.

leodangelo

Update: So i had the dealer do the software update for 250.00. I'm going to do the rest of the work myself. So far the car has not misfired after two days of driving. Previously it was misfiring all the time. Strange. I will keep you all posted on wether the misfire returns or not. I'm still sceptical but so far so good.

-LeoD

leodangelo

Update: My car is still misfiring. Took it for a spirited run. As soon as the coolant temp hit 98 degrees, I stopped and let it idle and it began to misfire. This time it misfired on 7,9,11,8,10 and 12. All the rear cylinders. I guess I'm going to bleed the intercooler circuit (I recently had my pump replaced). Any other ideas?

-LeoD

graytalon2000

Those are all left bank (driver's side) cylinders. Coil pack?

slonar21

read this
https://mbworld.org/forums/m275-v12-...elaration.html

MooJohn

We could add a mention that if the misfires happen at idle, it's the coil pack or ignition transformer.

If it requires driving at part throttle before the misfires occur, look elsewhere first.

leodangelo

At this point I believe it is probably my coils. I checked the service records and the coils are the original coils at 78k. So I ordered coils, plugs and insulators. Hopefully I can get this done this weekend. I will also be installing a killer chiller (planning on getting a tune once I get my car straightened out). I will update here with results.

-LeoD

leodangelo

So this weekend I decided to tackle replacing my coil packs and plugs. I ordered the coil packs from auto zone.

I just removed the driver side coil pack and I'm not sure I like what I see. The part # is the same as the one from Auto Zone and it looks pretty new. The insulator boots are clean and soft. I would have expected the insulator boots to be worn a bit. The plugs look original. There is no oil on them.

Any advice? I have attached some pictures of my progress.

NEMES1S

Did you ever get anywhere on this?

biker349

what about the ignition module?

NEMES1S

I also noticed today that the interior lights dim when the misfire hits. I am assuming it is a coil but I will dive init it tomorrow.

leodangelo

My issue turned out to be a bad coil pack. I replaced both coil packs and plugs and the issue appears to be gone.

If you are handy with a wrench doing the coils and plugs is not really that hard. I got my coils from Auto Zone. Over all I saved a lot of $$$ over dealer pricing.

-LeoD

NEMES1S

I did see just a tiny bit of oil around where the plugs seat but I don't understand where it came from

leodangelo

Was it on the passenger side? It might have come from 'spills' while filling the oil. I know my cam housing had a significant amount of oil on it from spills.

-LeoD

NEMES1S

it was driver's side. The filter housing isn't terrible far away but I think that the oil making it that far is a stretch. I didn't see any on the insulator or coil so I'm thinking there is something else. I am still trying to work through getting another warranty on this. It might be the only way I keep this thing