HangtimeDMV

Ok so my 2003 CL600 misfires at around 4000 rpm. I have to restart my engine for the misfiring to stop. I believe it is the coil pack or the spark plugs causing the misfiring.

The question I have is should I just go to the dealership and pay for the fix? Or an independent dealer? Ive heard removing the coil pack isn't simple and must be handled with care. I know a few good indy shops in the DC area but I'm not sure if this is the job for them. So id love input on that.

2nd question is are these V12TT engines safe to run thru a carwash tunnel. Im always scared of excess water getting into the engine possibly affecting my engine. How do you guys go about washing your cars?

Im new to this forum so any extra input not involving those questions are appreciated as well !

tusabes

Besides the coil pack it may be the ignition voltage transformer between the banks of cylinders on top of the engine

There is a service that will rent you good used parts so you can confirm which part is bad

http://www.v12icpack.com

If you can DIY I would try them

HangtimeDMV

Yea im not good with auto work at all. I have an appointment at the dealership tuesday so they can look and see whats causing the problem. I may just let them fix it if the price isn't too bad for the job

renault12ts

I doubt any water will get near your engine. Or, in any case, no more than on a wet highway.

Jack_88

You're good with the car washes, provided you still have your belly pan. If you're not handy, there's not much anyone can do to help you diagnose with that symptom. There are a number of suggestions of varying probability, ranging from plugs, coils, inverter, vacuum leak, fuel pump or filter, numerous sensors, and so on. The dealer will charge you around $180 for diagnosis(I've been to Silver Spring, I'm not sure about Tyson's corner or whomever you use.) Repair will vary upon the diagnosis, but if it is the coil or inverter, be prepared for what will definitely be a high price.

HangtimeDMV

Ok cool. And yea I'm prepared to spend a few thousands because I know it won't be cheap.

HangtimeDMV

Took it to the dealership and they say everything is working fine. I dont understand why can iNot accelerate at an extremely high rate if everything is fine ?

Jack_88

If it's not working right, everything is not fine. There's a difference between everything is all right and we can't find anything. I'd be a little disappointed that the dealer doesn't seem to want distinguish that.Does your check engine light come on? If not, I'd suggest replacing your fuel filter. A plugged up filter can result in starving the cylinders at higher RPM and not throw codes. If it hasn't been done or you don't know, it's a good maintenance item, at the very least.

HangtimeDMV

Yea the engine light comes on and I get misfire codes.

They said everything looks ok and they don't see a problem. They just cleared the codes. They also said it could be the spark plugs but iDont want to replace 24 spark plugs for nothing if it won't guarantee a fix if you know what I mean. They also say the cpu didn't show any error with my spark plugs but I'm at 76,000 miles and spark plugs normally need replacing after 60,000 miles or so, so that might be the issue idk.

Jack_88

Do you know which cylinders it was misfiring? If the spark plugs have never been replaced, you are due, and should replace them regardless. I still say you should also be replacing the fuel filter as well. Speaking of fuel, has the car recently spent a while sitting or had anything other than premium put in it? Do you use top tier fuels or just whatever station you happen upon?

tusabes

Sounds like the dealership just hooked up ther computer and did not try to replicate the problem by driving it

HangtimeDMV

Exactly. They said there was only one misfire so just cleared the code and told me that "If I wanted to they would replace the spark plugs." Other than that the car is in great condition.

I use 93 premium gas. and the car has been driven very frequently. Ill replace the fuel filter and take it to another shop to see if they would atlas look at the coils and plugs. Hope we can get this thing diagnosed. Im tired of being so easy on the gas lol

biker349

on the fuel issue, you might try adding techron, or another fuel additive to your tank and see if it improves. if you still have the cel after they cleared the codes it could be as stated fuel filter, or pump, bad gas, spark plugs, coil pack, or ignition voltage transformer. so there are a lot of things to look at. if it were me i'd first get the gas level low and refill and add a cleaner like techron and drive it for about 1/2-3/4 of a tank and see if that helps. then i'd go through the check list.
good luck

HangtimeDMV

Ok so now I'm taking the car back the shop I started with, Benz Elite in VA. They test drove the car a few weeks ago when it first started happening and told me pretty much that the CL V12 engines when pushed to the limit, can misfire and the codes he got weeks ago was that every cylinder was misfiring. The codes I got yesterday indicated it was cylinder 1 and 4 tho.
I don't even feel like I'm halfway pushing it to the limit tho so he says he will look at it again and we "might have to do process of elimination starting with the spark plugs. Then coil pack etc.

I will keep you guys updated but I'm determined to get this car back running like new no matter the cost lol.

Jack_88

If all cylinders were misfiring, the coil packs are unlikely. The voltage transformer is a candidate, though. Be very careful, it sounds like you may have gone to the kind of shop that will replace parts until the problem is fixed instead of diagnosing the issue. With this kind of issue, you can run up a $10,000 bill before they finally guess right. And there are a lot of places that are more than happy to let that happen.

Edit: The notion that a Mercedes V12 will misfire when pushed is flat wrong. It will only misfire noticeably if something is wrong. You will get misfire codes from time to time, but this is more than the occasional random code. You are describing a loss in performance, which means something requires repair. That they suggested that makes me even more suspicious of their diagnostic capabilities. Go somewhere that will do the proper diagnostics. I'm in the DMV as well, but I haven't had to find a good shop yet, so I can't tell you whom you should see.

HangtimeDMV

Yea im not going to go that far. My appointment is on monday, But the dealership and the shop both believe the car is in great shape because they see nothing wrong when diagnosing it. This is a place that many ppl take high performance vehicles like AMGs, V12TT all of the above.

Ill give them one more look at it because they do seem very knowledgable. But if we can't figure the exact root of the problem ill start with a new fuel filter and spark plugs, since there is no history of new spark plugs on the vehicle anyways and I'm almost at 77,000 miles.

Jack_88

That's the safe bet. You'd be replacing things that are probably good to do any way, and if your issue clears up, all the better.

HangtimeDMV

Exactly. Lets keep our fingers crossed.

tusabes

You should rent the coil packs and ignition transformer from v12icpack.com so you have them at the ready if the plugs don't fix it

Then you can have them immediately swap in the rentals and see if that fixes it

After the plugs are done , if it's still having issues, First swap in the rental transformer and if that doesn't cure it , swap the rental coils one at a time till you pinpoint the issues

HangtimeDMV

Ill probably do that if the plugs don't fix the problem. How much to rent ??

ItalianJoe1

My car isn't acting up nearly as bad as yours but has similar mileage and still the original coils and ICM, i'm sure it's on original plugs. I plan to throw a set of plugs in there first and see how that goes, then probably the ICM next as when I get misfires on hot restart, they seem to be spread across both banks.

tusabes

Look at the website I linked it lists the details and costs

HangtimeDMV

ok I see it @tusabes

Yea im not so sure all of them were misfiring. He went on a test drive and came back. The codes were cleared. I think he was exaggerating honestly. @Joe

HangtimeDMV

So I took the car to the guys at BenzElite in VA, they're changing the spark plugs and the tech told me the plugs were some off brand plugs and didn't look to good so the new plugs should make a big difference hopefully fixing my issue. Also getting the fuel filters fixed. I get the car back later today around 4:30 pm so hopefully everything goes well. Ill keep you guys updated.

ItalianJoe1

Good to hear. Are the coils orginals? If the plugs have been done there's a good chance the coils have been swapped out also. Just curious.

I have a random hot-start misfire that I need to address, gonna do as you're doing and start with plugs and maintenance, and maybe an ICM if it persists.