E5Fly

Hey everyone,

I have a 2011 E550 Coupe with 75,000 miles. Two weeks ago car was running great, next morning I let it warm up like always, drive about a mile, come to a stop sign and it's starts with a rough idle then CEL came on. Ran a code for cylinder 5 misfire. Went home, changed the plugs, still no luck..changed cylinder 5 coil pack and even tried to swap coil packs to the see if the code would follow and added some sea foam to the tank, still no luck..

Took it into Mercedes, they have had it for over a week now. Multiple compression tests, and a bore scope lead them to believe I have a bunch of carbon build up. They did the MOC optimizer to clear it out, still didn't work.

I'm going to pick the car up in the morning and put some BG 44k in. If that doesn't help I'll be taking the car to another dealer for them to pull the valve cover and check the cams, they said they are most likely going to have to pull the heads to clean out all that carbon build up..not cheap at all..

Anyone else ever had a problem like this or any tips? I've only put 20,000 miles on the car myself and never had any problems. I've always put 93 octane in and done my service on time. Wonder if the person before me wasn't using the correct gas? I've attached some pictures they sent me from the bore scope and have no clue wth I am looking at. Additionally the last pic says the leak compression tests shows 30%. Thanks in advance for any helpful responses.

-Austen

400ixl

Not heard of this being an issue.

What do yu mean when you say let it warm up? You should start the car, let it idle for maybe 20-30 seconds and then drive away. Just avoiding high revs until the oil is up to temperature.

Letting a car idle to warm up before driving away is not god for an engine. But even then, shouldn't cause carbon build up issues.

E5Fly

Hey Stu, yeah it doesn't take long, I don't actually let the car warm up to full temp, just about 20-30 seconds like you said, usually idles around 1,000 Rpms then drops down to about 600.

400ixl

That shouldn't cause any build up. Lack of detergents in fuel could be a cause, but even that shouldn't have that much effect.

Wrong temperature spark plugs could also be a contributor.

Are they saying that the valves are not sealing due to the build up?

2150john

I would run a can of Seafoam through the gas tank. Then run a half can through the engine using a vacuum line to suck it into the engine before I spent big money to have it decarbonated.

If you are not familiar with Seafoam do a Google search. It is the only "Snake Oil" I have ever used that worked.

E5Fly

Yeah I think so, it says the compression leak down test was at 30%. Last I spoke with the service manager, they said the next step was to pull the head to remove the carbon build up. When I picked up the car yesterday, it says they wanted to remove the valve cover and inspect the cams for damage..

E5Fly

hey there, thanks for the response. The day I changed the coil and plugs I ran seafoam through the tank. Yesterday I bought a can of the spray since I couldn't find BG 44k anywhere. We ran the line from the can into the throttle body like it says, didn't get any smoke out of the exhaust or anything and still having the misfire. Do you know where the vacuum line would be located you are talking about on on the M273? I was wondering about spraying some pb blasted or wd-40 into the cylinder through the spark plug hole and letting it sit for awhile? Thoughts?

2150john

No I don't know where to find the vacuum line on the e350. I will take a look under the hood of my 2014 and see if I can spot one. On most cars there is a line to the power brake booster. However I would guess the brakes on the e350 are electronic. If you didn't get white smoke out of the exhaust then you haven't gotten anything into the top end of the engine. I wonder if putting seafoam in the spark plug hole would do anything?

E5Fly

I Appreciate it, I found the vacuum line running into the intake manifold, I'm gonna go pick up a couple more cans of seafoam. I'll let you know how it turns out.

Flash Gordon

Not all gas are the same even with the same octane. 90K miles are a lot of miles if the previous owner use "cheap" gas even with the correct Octane. Cheap gas simply don't have enough detergent and other additives to keep the engine clean. My previous G35 had 120K before I trade it never had any carbon buildup.

Suggest after you resolve this issue, use Top Tiers gas. Do a search to see which gas companies sell Top Tier gas in your area.

E5Fly

Yeah I've never heard of this problem before or had it in any of my other vehicles, it seems Shell is one of the better fuel stations for having detergents.

nauticalx

OP, did you buy the car used? Couldn't this be a result of lack of regular oil changes? Do you know that previous owner did regular maintenance on the vehicle?

Or- am I confusing carbon buildup with sludge buildup?

E5Fly

Yeah I bought the car used may 2016. It's possible, the car was from New York. From what I remember it was serviced regularly. I tried the seafoam again, nothing has worked. Today I'm dropping it off at a shop, they've made appointments with the machine shop, they'll go ahead and pull the heads and clean it all out. Mercedes wanted $5,500. I'm having another shop do it for $3,500, they said they can have it done in about a week. Guess we'll see what happens.

PaulE550

Does the other shop that you are taking it to regularly work on Mercedes or other German brands regularly? The reason I ask is some local shops might cut you a really good price, but they have no experience working on certain brands and as a result end up causing more problems than what they tried to fix. A good indie shop that specializes in German cars in general should be OK though.

E5Fly

Yeah the shop is familiar with German cars, the work also comes with a warranty if there should be any issues.

cmlf1

I run Lubro Moly valve cleaner (ventil sauber) and in a different tankful their injector cleaner (or Techron if LM isn't on the shelf) before each oil service. Best available products to keep things clean. I have done the "hot soak" numerous times with the valve cleaner on older M30 engine BMW's with good results, usually right before valve adjustment. With modern engine management systems and fuel this should no longer be an issue, but obviously something is leaving deposits.

Carl
2010 E550

E5Fly

Sooo the shop had been waiting on gaskets and parts to come in before removing the heads. Got all the parts in and was notified yesterday that they ran a compression test and vacuum test. They don't believe the original diagnosis from Mercedes on the carbon build up is correct and said the vacuum gauge was dancing around leading them to beleive it's a piston issue and most likely the piston rings. They said I was losing compression on all the cylinders on that side, however can this happen just all of a sudden? Car has never overheated or been red lined, I don't drive it hard and keep it maintained, also the engine doesn't use oil or shoot smoke out the exhaust nor do I have oil all over the back bumper like cars I've seen with bad piston rings and the car ran fine, never noticed a loss of power...can this happen all of a sudden and cause misfire? They said it was most likely because these engines go so long without oil changes is what can cause piston rings to break down...thoughts anyone?

They ordered a new motor and can have it installed for not much more than what it would cost to clear the carbon build up, engine has 18,000 miles and comes with a 3 year 36,000 mile warranty. I'm really just in shock from this whole ordeal. I find it to be unheard of especially at 75,000 miles..

PaulE550

Sounds like the previous owner either didn't maintain the car properly, cutting corners whenever possible and using whatever was the cheapest (gas, oil, etc.) or really abused the hell out of the vehicle a lot. These cars are built to be driven hard, but they also require that all maintenance be done properly. Just like any other performance luxury vehicle. Your engine should have been good for at least 150,000 or more, if properly maintained. Clearly the previous owner didn't.

mcleantmw

Any updates for the replacement motor install?

Also, curious where they obtain the replacement engine?

yaknart33

This is an old thread ,but the issue of carbon build up is still a problem on most car makes.Its due to the design of the intake system

including the valve train.Emissions control systems help create this problem.I have run into several problems with carbon build up

causing missfire.One particular vehicle did this most days on cold start .I verified the problem was mechanical with a vacuum guage on

it .When started the vacuum guage would show a consistant rapid drop indicating one cylinder was not operating.A running

compression test will show this concern but only when its happening.The vacuum guage test is non invasive test that is very

accurate.Luckily for the owner I was able to let the vehicle sit and soak with intake cleaner and intermittant cranking the engine with

plugs out and ignition disabled. At end of the day changed the motor oil due to the cleaner soak ,cleaned plugs restarted vehicle

several days in row and miss never came back.I also had cust use fuel cleaner to help keep it clean.The carbon build up can

completely cover the valve with carbon causing it it stick open,a very common concern on virtually every vehicle.

Chevota

I'll add to yaknart33's comment and mention the PCV system dumps oil vapor into the intake which is where most all the carbon on the back of the intake valves comes from. This is fairly common knowledge but the newer direct injection engines cannot clean the valves because no fuel washes them. So when I bought my first direct inj car (used) I was in there pokin around and noticed the throttle blade and surrounding area was dripping wet with oil. This was a '13 E350 btw, and looking past the blade the intake was drenched! This is not good.... It's supposed to have an oil separator but clearly it doesn't work. My guess is it wasn't defective, just ineffective as all car oil separators are.
Part two of my story is preventing that oil from getting in there in the first place. I posted my findings here, which is basically a warning about aftermarket oil catch cans and my/our need to do something to stop said oil. Also explains how I made my paper filter:
https://mbworld.org/forums/c450-c43-...-engine-2.html
My post is #26 on 3-15-20
I've seen other oil separators for various things and ALL the centerfugal ones I've seen do not work! I have one at work that does but it's huge and uses an actual filter element.

yaknart33

The carbon buildup is fuel related ,not oil ,the fuel is not completely burned causing a buildup on the valves.Thats why it affects the intake valve more then exhaust valve.If it was from motor oil it would affect both valves and you would have blue smoke from exhaust.As you can see when it gets real bad the carbon can chunk off and cause engine damage .The carbon can cause driveabilty problems as it affects air fuel in the cylinder,the fuel /air mixture is designed to swirl into the cylinder with good mix of air and fuel.The carbon in intake causes air/fuel to tumble into the cylinder causing incomplete combustion and more carbon.It will cause hesitation,stalling,missfires,poor acceleration.If you use a intake vacuum port to ingest a liquid like sea foam be very carefull ,if you put to much in it can cause hydrolock and seize engine when the connecting rods bend .They make tools to regulate the cleaners to a set flow rate to reduce that possibility .Do it slowly .Adding fuel additive on long trips works also. Dealers used crushed walnut shells to blast the valves with heads on . e more then exhaust valve.The intake valve is cooler allowing carbon build up.