Pulled into the garage last night and saw the CEL was on, and engine was running rough.
DAS shows misfire fault codes on Cyl's 4 and 7.
But it's running smooth now.
I cleared the codes, CEL is off and engine is back to normal. CEL did not return (yet).
I imagine this may have a variety of causes, possibly as simple as a bit of water in the gas.
But I have some concern that if it was leaking fuel injectors, now there is the potential of burning up the Cat's (Ohhh $$$$).
But whether its injectors or coils, it's hard to see two going at once. The plugs are pretty fresh.
Any thoughts on how I should proceed?
Thanks, MK19

 

How many miles on the car? When you got new spark plugs did you get the right ones? Did you replace the wires set at the same time? If not, those are 23 years old now
The NGK Laser Iridium come pre-gapped
I replaced all 16 plugs and wires in my 2003 SL55 and later asked a MBZ dealer how much they charge toi do this job - parts and labor and they replied $3,950.00 USD (plus tax). Is that ridiculous, or what!!!

 

I believe I did use the correct ones. I used NGK Iridium LFR6AIX-11, gap ~.031”-032”. There isn't any spark plug wires as I recall, as the coils plug directly on to the plugs. I paid $50.40 for those plugs on Amazon, so yes, $4k is absurd. I'd guess the use an MB labeled plug that cost $30 each, but still, nuts. Find a good Indy..........even a poor one could change the plugs. The coils are very likely original. Car has 86k miles.

 

Many of the spark plugs on Amazon are counterfeit, sometimes even those listed as sold directly from Amazon.
And more more vid and articles. Buy your plugs, sensors, etc from a local parts store.

 

Very interesting, Thank You.
I drove it about 30 miles out and back with a 2 hour rest in between last night..........no problems, so hopefully just a transitory fault. Fingers crossed is hardly a strategy, but that's where I'm at.

 

$50 for 16 spark plugs?! What??
Best way to buy those NGK plugs is directly from NGK on their own website, there those plugs cost $13.72 each. This way you know they are genuine NGK the ones the owners manual that came with the car, specifies (ILFR6A) # 3588. They also sell a wire set. If your car is a 2003 SL55 AMG with the M113K Kompressor engine thast does have 16 spark plug wires those are about ten inches long thaer would be one for each spark plug. Engine should take 16 spark plugs.

2003 SL55 AMG with M113K Motor!!!

An AMG motor should have one of these name badges on top
Very slight variations in length so when replacing wires match them up to the old ones and keep them all separate doing each one at a time so you don't wind up with the last ones being too long or short. My total parts cost was about $400 for plugs and wires, the wires I opted for were Bremi brand made in Germany. Other wirers cost a little more. Benz dealers charge a lot for the spark plugs, then rob a guy on labor, it's insane, apparently they're geared to doctors who know absolutely nothing about cars. I admit that the rear-most plugs are hard to reach, and when I did this job it took me nine hours, but only because my left shoulder was NOT working at the time. I did the job anyway, kinda dumb, but dedicated. Might have been a six hour job otherwise, because I work slow and try to make sure every step is done perfectly... so I don't have any screwups. I should have asked ther Benz dealer how many hours labor they are trying to bill for!! I have bought headlight bulbs for my S-Class on Amazon those even come with a Sylvania hologram of authenticity and a website where you can enter the liight bulbs serial number to "authenticate"... the website itself was FAKE!!! It all looked almost real, but tiny chinese writing you could hardly see, made me wonder. I called the real Sylvania, they gave me their real website. The bulbs I had bought were fake!! I retuned those to Amazon, and gave a bad review, the amazon seller was angry to about Level 9. Kept defending himself, I was like You're aFraud. Bought real genuine Sylvania light bulbs and verified with the real Sylvania. Those chinese light bulbs may even have been "okay" and worked, but the real light bulbs cost about $60 so why try to save 20 bucks getting crap, especially when sold by liars and deceivers. Fake bulbs probably wouldn't last as long as real ones either. The M113K has eight ignition coils; Each ignition coil powers two spark plugs, and has wires about 9 inches long going to the plugs. NGK sells these ignition coils at $54 each. They sell a wires set for $327. Partsgeek sells the Bremi wires set for $184. They also have another Bremi set for $158

 

Great to know that NGK has their own website for ordering spark plugs and even coils and wires.
I'm very active on (and moderate) a GM tech site and the proliferation of counterfeit Bosch, NGK, Denso, Delphi and ACDelco parts on Amazon and eBay has gone through the roof. Plenty of posts where the OP has already replaced e.g. the crank sensor (with an Amazon parts) three times and still has symptoms. Its not until we convince him to buy the part from the dealer or good parts store that the problem is solved. Spark plugs, sensors and injectors are among the most commonly counterfeited parts. Especially dangerous are bad injectors which could hydo-lock an engine.
I used to believe that if Amazon was listed as the actual seller on Amazon that the parts would be genuine, but recent articles indicate this is no longer true.
I'll have to confirm, but I suspect major mail order auto stores like Summit Racing and Jegs would be good sources of genuine parts. Both also sell through Amazon which is good because otherwise they have a $100 minimum for free and super fast shipping.

 

I'm sure that Summit Racing and Jeg's are reputable and will not sell any fake stuff. Also Rock Auto, FCPeuro, AutohausAZ, there's a bunch of great parts sellers. Amazon at least has good returns policy most of the time.But If I can I try to get from real companies that specialize in parts

 

Tonylinc, that uTube was very helpful. I pulled the #1 Plug and see that it has no lot number, and also that the electrode appears too warn and the gap had increased by .003-5", way more than I'd expect in the 12k miles since I changed them. So, it's new plugs, with wires this time.
I'd change out the coils too, but that smells like $$$.

BTW: Have driven it several times now.........no misfires.

 

Special thanks to mrvedit for that Yootoob video. I was aware of fake headlight bulbs, but didn't really give thought that they'd make fake spark plugs!!!
Unbelievable whirled we are living in. How much tooling does it take to gear up and produce spark plugs!!! I'm sure glad I've bought mine direct from NGK for in fact, all the cars. I was really amazed at the distance they went through, to establish a fake Sylvania authentication website for their Chinese knockoff headlight bulbs. Any parts you buy, you should buy strong reader glasses magnifiers and examine eavery surface of those parts looking for chinese writing! LoL. AND the packaging.
Sensors for these engines, equally important!!!
I'm sorry to hear that the OP here had bought counterfeits, if it were me I'd order certifiably good stuff very soon and replace soon as well, even if the car is mostly running fine. Just to treat the engine right. I'd be angry about having to do the replacement job all over again, I mean it took me a whole day, and of course I was sore for the next day... If bought those counterfeits from Amazon even if it's a month or three later I would complain and try to get a refund, when you get no service (which is most often), I have always had good service when I emailed direct to jeff@amazon.com ~This was back when jeff B. was still CEO, but that email is still responded to.

 

For a 2003 M113K engine the exact plugs to get are NGK Laser Iridium, ILFR6A, 3588.
One can compare price between NGK dot com and FCPeuro dot com, I am certain FCP won't sell fakes, and they may buy so many that they can sometimes sell for a little bit cheaper than the NGK website.
For my S-Class 2008 S550 (M273 engine) I bought all new ignition coils, Delphi brand, from Amazon, at the time they cost $30 apiece. I was happy with what I received and they looked all genuine. BUT a few months after installation, suddenly the car began to run badly. Determined that one of the new coils had failed!! I wonder now if they're counterfeit, it's been a few years now with the car running perfectly though. Luckily I save all old parts, labeled in a box, so I took the best looking one of the "old" coils and put that on the car. Still running beautifully today.

 

Yes I added coils too. Bought it all including the plugs and wires from PartsGeek. $344. Aftermarket coils and wires. Full pop$ on the plugs but I'll still look for the lot #'s.

 

I have had good luck with Partsgeek buying genuine MBZ parts.