Spark plug indexing?
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Just make sure to buy from official sources to prevent yourself from having to deal with counterfeits which could potentially destroy your engine. You could also buy from FCPEuro but not all brands sold are pre-indexed, perhaps another forum member can confirm. If in doubt, feel free to ask the FCPEuro staff by calling or using their live chat.
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See post #16 at https://mbworld.org/forums/s63-amg-s...-mb-bosch.html
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Circling back to this and just wanted to leave some comments in case someone else had the same question. So I am using the OE spark plugs and was told from multiple sources that they come pre-indexed. Meaning you just screw them on and it will align correctly. From what I've researched, the gap part should be pointing towards the fuel injector side with a tolerance of 45 degrees either side. But let me tell you that all the plugs were pointing in all sorts of directions as if they're not indexed. I tighten them down to 22/23Nm. So I am not really sure what to make of that. I just hope this won't cause any major issues.
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Some will say its the end of the world, because Mercedes says so. And that may be true.
Others, will claim the opposite.
Either way, you might be fine, Jen. Maybe... circle back with us in a few months and tell us how it's doing?
Others, will claim the opposite.
Either way, you might be fine, Jen. Maybe... circle back with us in a few months and tell us how it's doing?
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Too bad you didn't inspect the plugs prior to installation and compare the position of the ground electrode with respect to the plug's threading. Maybe we're all being taken for a ride on this indexing thing.
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Never really bought into the whole indexing thing. We're talking about a combustion chamber that fills with air and atomized fuel on the intake stroke, then gets ignited after the compression stroke. All of that A/F mixture is already... well... mixed before the spark plug(s) fire off. So, pointing the electrode gap right into the injector stream really makes no sense to me. But then again, maybe I'm being over simplistic about the whole thing, since I'm not an ICE ignition engineer.
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Never really bought into the whole indexing thing. We're talking about a combustion chamber that fills with air and atomized fuel on the intake stroke, then gets ignited after the compression stroke. All of that A/F mixture is already... well... mixed before the spark plug(s) fire off. So, pointing the electrode gap right into the injector stream really makes no sense to me. But then again, maybe I'm being over simplistic about the whole thing, since I'm not an ICE ignition engineer.
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Never really bought into the whole indexing thing. We're talking about a combustion chamber that fills with air and atomized fuel on the intake stroke, then gets ignited after the compression stroke. All of that A/F mixture is already... well... mixed before the spark plug(s) fire off. So, pointing the electrode gap right into the injector stream really makes no sense to me. But then again, maybe I'm being over simplistic about the whole thing, since I'm not an ICE ignition engineer.
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2018 C63S AMG Coupe, 2019 Jaguar F-Pace SVR
I get it that AMG recommends it... But I would love for someone to explain how not indexing a spark plug can "destroy an engine". There are literally millions upon millions of cars and trucks on the road without indexed spark plugs and they are all doing fine. Perhaps indexing might give you 1 HP more, or .01 MPG more?
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Try asking Mr. Google:
what is spark plug indexing in amg engines and how is it done
I'm guessing the "danger factor" has to do with flame propagation and component positions. However, regardless of what "people on the internet" say, I'd bet on the wisdom of the engineers at AMG who designed the engine and set the maintenance procedures. While I might push some things, when a very costly engine is involved, I'd take the (seemingly reasonable) extra effort to do it "correctly." It's a simple "cost vs benefit" analysis with (to me) an obvious outcome.
The shop foreman at my (excellent) dealer's service center once shared with me (because he knows I'm a software geek) detailed information on the ECU's adaptive "spark management" that's common to the various V8 engine variants. As I'm sure any of the serious tuners will tell you, it involves a significant number of factors with amazing precision. That's an essential part of how these engines can achieve such a huge dynamic range. My GTR Pro gets about 4.5 MPG (imperial gal) on the track yet gets >23 MPG running briskly on the 400+ km (250 mi) trip from the west coast, over the rocky mountains and on to the track. That's a dynamic range of over 5:1! Amazing.
what is spark plug indexing in amg engines and how is it done
I'm guessing the "danger factor" has to do with flame propagation and component positions. However, regardless of what "people on the internet" say, I'd bet on the wisdom of the engineers at AMG who designed the engine and set the maintenance procedures. While I might push some things, when a very costly engine is involved, I'd take the (seemingly reasonable) extra effort to do it "correctly." It's a simple "cost vs benefit" analysis with (to me) an obvious outcome.
The shop foreman at my (excellent) dealer's service center once shared with me (because he knows I'm a software geek) detailed information on the ECU's adaptive "spark management" that's common to the various V8 engine variants. As I'm sure any of the serious tuners will tell you, it involves a significant number of factors with amazing precision. That's an essential part of how these engines can achieve such a huge dynamic range. My GTR Pro gets about 4.5 MPG (imperial gal) on the track yet gets >23 MPG running briskly on the 400+ km (250 mi) trip from the west coast, over the rocky mountains and on to the track. That's a dynamic range of over 5:1! Amazing.
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@user33 Mr. Google is often full of BS curated by many many "experts" who all are more than happy to declare their knowledge is the only knowledge. I'm not debating that indexing can have negligble performance benefits, but I am doubting that not idexing spark plugs can "destroy an engine". My assessment is supported by the millions and millions of vehicles with non-indexed plugs that are just fine.
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@user33 Mr. Google is often full of BS curated by many many "experts" who all are more than happy to declare their knowledge is the only knowledge. I'm not debating that indexing can have negligble performance benefits, but I am doubting that not idexing spark plugs can "destroy an engine". My assessment is supported by the millions and millions of vehicles with non-indexed plugs that are just fine.
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MY17 C63s Sedan
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Mostly out of curiosity, but partly out of eventual need, I ordered a set of MB sparkplugs p/n 0001590500 that fit the M176 engine and several others. Autohausaz's price was $22/ea for the MB branded part, but only $17 for the NGK version and $13.50 for the Bosch version, both which are sold under the MB OE p/n. The MB branded plugs I received have the NGK p/n SILZKFR8E7S stamped on them, so they're probably the same as the $17 NGK plug sold under the MB OE p/n. Autohausaz also sells this SILZKFR8E7S NGK branded sparkplug for $22/ea (go figure).
The curiosity part of my purchase is whether these plugs are manufactured to be identically indexed. Stay tuned -- I'll post a follow-up.
The curiosity part of my purchase is whether these plugs are manufactured to be identically indexed. Stay tuned -- I'll post a follow-up.
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Well my car was misfiring on cylinders 7-8. I replaced all the spark plugs. 7-8 still misfiring . I replaced just that injector and worked for about 2 months. Now cylinder 4 is misfiring. Happens Intermittently. Usually I start the car in the morning and it's fine. When it "warms up" it will start.
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
Last edited by Barbalatte; Sep 6, 2025 at 06:18 PM.
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Well my car was misfiring on cylinders 7-8. I replaced all the spark plugs. 7-8 still misfiring . I replaced just that injector and worked for about 2 months. Now cylinder 4 is misfiring. Happens Intermittently. Usually I start the car in the morning and it's fine. When it "warms up" it will start.
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,156
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From: Colorado
G550
Well my car was misfiring on cylinders 7-8. I replaced all the spark plugs. 7-8 still misfiring . I replaced just that injector and worked for about 2 months. Now cylinder 4 is misfiring. Happens Intermittently. Usually I start the car in the morning and it's fine. When it "warms up" it will start.
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
im suspecting it could be the indexing of the plugs.
car has now done 51,000km 2019 build year
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C63S
I haven't changed the coils. I don't think MB Australia recalled the cars for this issue. I think it was only for the US market.
in saying that, the injector was the problem with that 7-8. After we swapped out all the plugs, we did have a defective plug on Cylinder 6. We swapped it out and fixed the problem. I'm thinking it could be the same thing.
in saying that, the injector was the problem with that 7-8. After we swapped out all the plugs, we did have a defective plug on Cylinder 6. We swapped it out and fixed the problem. I'm thinking it could be the same thing.
