Hi All
Got my ‘15 S550 4matic in January at 62K miles.
Carfax service history shows car was very well maintained by local MB dealer
plugs were replaced at 45K miles.
In May experienced cylinder 6 misfiring (65K) and had my Indy replace the ignition coil.
Same thing now happening on cylinder 4 (67K).
Am scheduled Friday to have the rest of the coils replaced and be done with it.
I figure that two fails in two months is telling me that the rest of the coils are suspect.
Is this commonplace for coils to start failing at 67K miles/ten years?
My most recent MB (08 S 550) had no misfiring issues for the seven years I owned it. Bought at 72K, Sold at 133K.
I welcome any insight and advice
thanks a lot!

 

I have just 54k miles on mine and have had 3 coils replaced in the last year. Seems to be commonplace at this age. I just let my warranty keep paying for new ones when needed.

 

Plugs were replaced at 45K…
BTW..the misfire comes and goes.
I drove to my Indy while it was happening.
when I started the car to leave…ran like a top on the way home.
next start up? Who knows

 

With my last misfire, the CE turned off when I turned off the car and the code wasn't stored. Next time it happened I left the car running, threw my code reader on it, then took it to the shop a few days later for replacement. It didn't throw a code when I had it in the shop, but pictures of the code when it happened were good enough for Endurance to pay for that coil pack. Funny thing is I can sometimes feel slight misfires, so I know another one will be going soon and I'll have my code reader at the ready.

 

Ignition coils are NOT a major failure item. What is though is the rubber boot that the coil has on it. The boots are replaceable and cheap and when they wear out they cause misfires. A new coil comes with a new boot on it for WAY more money and solves the problem your talking about but of course the coil itself was not likely the problem as i mentioned. Something worth thinking about.

 

Thanks Katie..
Interesting info about the rubber boots
In my younger years, I would have done the job myself. I could replace the boot on each coil and see how it went.
These days, peace of mind is worth more than saving money.
I’m scheduled for Friday to have my Indy replace the remaining original coils.
As I stated in my post…2 bad coils in two months is enough for me to take care of them all at once and be down the road enjoying my car.

 

Thanks Dave.
The job to replaced the reaming 7 coils will be $900.
The peace of mind is worth it.

 

It’s not unusual for ignition coils to fail around that age/mileage, especially if they’re original. Heat and wear take a toll. Since two have already gone, replacing the rest is a smart move to avoid future headaches. Your ’08 was likely more robust or had coils replaced earlier. Stick with quality parts (OEM or reputable brands) for longevity.

 

Yea but those two bad coils were more than likely two bad boots.............. thats kind of what I was saying. One can clearly do research and discover that coils themselves are NOT a big failure item BUT of course a shop that wants to make money wants to sell the more costly repair. Case in point on my AMG GT i got the misfires. The boots were like 12 dollars each so 96 dollars. If i were to replace the coils thats four of them at least 1000 dollars total. So for 1/10 the cost I fixed my misfire problem and all is well.

 

Interesting post! I changed half my boots recently with the newer ribbed kind (MBZ A177 159 14 00) that may seal the plug bores to reduce oil problems.

Oddly enough, the car seems to run noticeably better with the four new boots (and taking a little weekend trip). Gonna do the four remaining boots over the weekend and now look forward to seeing how it runs with all eight in place.

 

@Katie22 Do you have the part number for just the boots for the 4.7L motor? And how tough and time consuming of a job is it to swap out the boots?

 

While I am surely impressed with your diagnostic skills and knowledge, I also don’t care to engage in pissing a match about what I should, or should not, do.
As I said…in my younger years I would have done the job myself…playing around with coils, boots, etc would have been an interesting endeavor.
However, at 77…I don’t want to mess around with it, one way or another.
My wife and I established a very comfortable retirement by being smart with our money. Scrimping here, saving there, etc.
At this point, we relax and enjoy the fruits of our labor.
Quite frankly, going to your measures to save $500 is on what is, at best a “very likely” cause, is not on my radar anymore.
Regarding shops that take advantage of naive clients. Yes those exist. I have used my Indy for 25 years and trust them implicitly. I discussed the “bad boot” culprit with them. To get to the point of checking and replacing worn out boots will take the same amount of labor as replacing all of the coils. So how I’ve gone from “very likely” to the peace of mind of having new coils all around.
BTW…I would be leery of who ever is charging you $250/coil. I’m am paying $76 each. You could “very likely” be working with one of those shops that make money by over charging for parts. I’m getting 7 coils replaced for a grand total of $908…
Anyway Katie…to quote Bob Dylan from 1966:
”You go your way and I’ll go mine”

 

I hear you. I really dont care what you do. Part of this post is to help other people that are willing to consider things like this. Case in point since rubber degrades over time in a hot environment people will do just as you and replace the coils thinking that is the problem. They MIGHT buy an aftermarket coil which might be junk and that is a terrible thing to do IF there is nothing wrong with the OEM coil except needing the boots replaced. THIS IS EXACTLY WHY I posted what I did. You certainly can spend all the money you want and yes indeed it does cost the same to change the boots in labor as it does to change the coils and that is exactly why the shops say to change the coils. But if the job is very easy then doing it yourself is quick and painless. ON my 2016 MAybach each coil was held on by a screw and I had to remove some turbo tubing to get at all the coils. ON my AMG gt its even more of a challenge to get the coils out BUT then I know the job is done correctly as per Mercedes WIS directions and I dont have to worry about some mechanic fighting flat rate garbage pay to get the job done hopefully correctly.

Guess the point that you choose to ignore is that ignition coils are a LOW failure rate in cars and certainly can be researched to verify what I am saying. BUT the rubber boots well thats a different story they fail often enough. IF someone were to come up to me and say my car has 50k miles on it and I am going to replace the fuel pump I would be saying the same thing. Fuel pumps dont generally fail at 50k and worse if someone buys an aftermarket fuel pump to replace a perfectly good fuel pump with 50k on it their nightmare could just be beginning.

Someone asked me the part number for the coil boots. I do not have that and my Mercedes WIS expired so I cant access it at the moment. I suspect you can look it up on the internet. ALSO you must carefully apply dielectric grease to both ends of the boot with q tip. This grease also helps to prevent the electricity from escaping the boot and causing misfires.

PS your leary about the 250 for a coil is because on the AMG I have FOUR coils and each coil runs TWO cylinders. 250 at least times four is 1000$ not counting labor. The boots were around 13 so for me it was WAY more than saving 500 dollars. More like saving 900.

 

I’m right there with you Alexie
Thanks!
Chuck

 

Thread cleaned up a bit. Good to see helpful answers whether they fit the need or not

 

Dave I do not have the part number for the boot for your engine. As far as time goes I did the job on my V12 which so I cannot tell you how hard it is BUT I am guessing you tube has videos that show you how to do it on your engine. Of course can also buy a copy of Mercedes WIS on ebay for used to be 10 dollars and all the factory service and parts manuals are then at your finger tips.

Most important thing is to apply dielectric grease to boots at both ends of the boots very carefully so to seal them. I used a Q tip..

Oh also any time you remove a coil to replace a spark plug you run a chance of damaging a coil boot and causing misfires thereafter. I ran into that when I changed the plugs on my GT but not when I did the Maybach. Go figure. From that point on when I change spark plugs I am very careful not to damage the boot and I usually replace the boots when I do the plugs just because they are cheap. And of course if I did not change the boots after I replace the plugs and I get a misfire I immediately replace the boots and problem is solved.

 

This makes sense. I did have my plugs changed in December and have had 2 coil packs replaced since then. I can see 10 year old rubber boots going bad/dry rotting and being the cause, especially since they had to work those old boots off to get to the plugs. Ever since the plugs were changed, it seems like there is a very slight misfire all the time, but it isn't generating codes.

 

Dave like I said my version of WIS expired BUt its cheap to buy on ebay. Also youtube might have videos of changing the plugs on your engine. With all that said you could probably remove the engine cover and look at the top of the engine and get a visual of the coils and come to understand how easily they are to remove. Some vehicles they are very easy and others like my AMG GT and Maybach it takes some time to get at them. In any case it is kind of fun to do your own work and learn something and of course you dont have to count on someone else doing the job correctly.

What's kind of funny about these boots that are worn out is often they have tiny holes in them and the car will run perfectly fine BUT when you give it some gas the turbos kick in and the check engine light comes on and you get misfires. As you might already know electric flow always takes the path of least resistance and when the pressure in the cylinder increases from the turbo the electrical path to cross the electrode at the end of the spark plug becomes greater than that tiny hole in the rubber boot and misfire. Of course when your not on the gas and cylinder pressure is normal the electrode path is often the easiest to overcome and no misfires.

By the way I found this video that might be your engine.

 

My 19 S560 made it to 92k before coil on cyl 4 failed.
It was 10 dg for 2 weeks when it failed.
Weather will help a weak coil along towards its final failure.

 

Coils are consumables. 10 year old coils should be replaced. You will be amazed at the improved startup crispness and idle smoothness.

 

Thanks Chassis.
The car is at the shop having the coils replaced. Peace of mind is a good investment.

 

The seven remaining original coils were replaced today.
The boots on each of the removed coils showed no signs of deterioration…no cracks, breaks or hardness.
They came off of the plugs just fine…the grease applied at the factory was still present and did its job

 

replaced today..runs great
As I said earlier…peace of mind is a good investment

 

They reused the boots? Wouldn't new boots have provided more peace of mind? I'm at 50K miles, and I plan to replace the boots when I replace the plugs.

 

no, the original boots were tossed along with the coils.
the new coils came with new boots.
I was just saying that the boots on the original coils do not look to be the culprit in the misfiring.
Katie 22 is quite adamant about replacing just the boots.