tziady

Hello all,

My car is having a cylinder misfire issue. I am thinking of trying to replace the spark plugs myself. What brand and the are recommended for a 2007 SL550. I see do many different options and brands and was hoping for a recommendation?

Thanks,
Tamer

Aussiesuede

Before replacing the plugs, have you swapped the coil pack from the cylinder you're receiving a misfire on to another cylinder to see if the misfire follows the coil pack?

As far as plugs, the Genuine Mercedes Part number is: 004159180326

And the Bosch Replacement Part number is : YR7MPP33

Both available in complete sets from: FCP Euro

Also, to cleanly remove the spark plug boots without damaging them, this tool is a godsend. Spark Plug Wire Tool

tziady

Thank you very much for the replay. So, just switch the Coil Pack to another cylinder and see if the issue persists to assess if it is that is the issue. I have not. I will do so. Thank you very much for the idea. I had not thought of that.

Also, would a six inch tool like this work well:
Again, thanks for the quick replay. I will try switching the Coil Packs and see if it fixes the issue tomorrow.

Cheers,
Tamer

tziady

Btw, do I need to do any gap setting? Or will the OEM or Bosch ones come set properly?

Aussiesuede

That tool is good for actual removal of the spark plugs. The other tool I noted is for removal of the spark plug wires boot so you don't risk having the wire separate from the boot.

Aussiesuede

Luckily our engines aren't hypersensitive to gapping,. So factory gapping is usually sufficient. That said,. It's always a good idea to test the gapping of new plugs to make sure they aren't too far out of ideal spec.

tziady

On that note, what is the ideal spec?

Thanks,
Tamer

Aussiesuede

Optimal = .040

Range = .039 - .043

tziady

Would these be good coils to buy in case I need to replace them? Does anyone have other suggestion of good coils?

https://www.araparts.com/catalog/pro...oaAit1EALw_wcB

tziady

or are these better?

https://www.fcpeuro.com/products/mer...il-gn1023512b1

Thanks for all your help.
T

Aussiesuede

All things considered, FCP Euro is the vendor of choice since they warranty their parts for a lifetime of ownership. If the coil packs go bad, they'll replace them for free. Can't beat their guarantee!

tziady

Last question. When replacing the coil pack. Do I need to replace them all at the same time or can I without issue purchase 1 at a time? In other words, does matching these coils a requirement?

Thanks,
Tamer

tonylinc

A 2007 SL550 does not have coil packs, it has one coil on top of each spark plug, easy removal, easy to replace plugs as well. Quite different from the V12. My owner book for my 2007 SL550 says to use NGK platinum plugs which are factory pre gapped you never re-gap platinum plugs. PLKR6A is what my owner book specifies, also a Bosch corresponding but I would not use anything other than the NGK myself. The coils can be bought for around $30 each. And take a minute each to replace if you're doing it at the same time as the plugs.

tziady

Thanks for the response. I may be using the wrong terminology. I did buy the NGK plugs. But I am also looking to possibly needing the coils replaced. Hence my question. I have an issue with cylinder 5. I have 8 plugs and can easily buy 1 single new coil plug. However, I was wondering if it is recommended to change all 8 at the same time or if it was not an issue. Again, sorry if the question seems silly. But I am wondering if buying all 8 new coils or just 1 is worth it. From the coils I listed up top from https://www.fcpeuro.com/products/mer...il-gn1023512b1

So, should I just buy 1 or should I replace all 8 while I am at it?

Thanks,
T

tonylinc

I replaced all the ignition coils on my S550 and also on my GL450 SUV, but at around $30 each there goes a few hundred dollars each time. If you know cylinder 5 is missing I would just get one coil and replace that one, you can always get more later. They're easy to reach right on top the engine. I have my "old" coils from both vehicles, kept them in the garage, I'm sure that most or all of those are still good. So now if I have one misfiring I can use some of those. You won't have any issue if you just replace one that's bad. If any others misfire then you can easily go back and replace that one or all.

tziady

If I am replacing the spark plug and the coil; I really shouldn't have to worry about that right?

I feel like I am missing something. I am very sorry. But I did buy that tool; but I am absolutely unsure of how and where to use it.

I disconnect the power connectors by unlocking the grey tab. I remove that wiring plug.

Then I remove the torx screws.

Then I pull off the coil - Is this where I am supposed to use that double wrench? I am sorry if this seems stupid. But I pulled one (#5) and it appeared to come out without any issues? Was I supposed to disconnect something else?

Thanks,

And sorry I am such a newbie.

T

**************UPDATE***********************

I guess my Mercedes Benz 2007 550 SL uses a direct ignition setup and does not need the wire removal that is used in some other models. From FCP:

Direct Ignition CoilDirect ignition coils are located directly over the top of the spark plug. In this ignition setup there is one ignition coil per spark plug and there are no spark plug wires. This ignition setup is often referred to as a coil on plug ignition system.

I am assuming this is correct for my setup.

Thanks for the help and please let me know if I am wrong.

Cheers,
Tamer

Tommyboy928

Everyone with old engines, and alot miles need change their spark plug wires, everyone talks about coils, when its very bad wires that is the issue . They actually wears out . we bought 10 mm race cables for 2 SL55 AMG and one CLK 55 , huge result on 2 of the cars one 2004 Sl55 with close to 100 000 miles, and around same miles on the CLK . was like another car owners say . On my car with low miles 38 000 not huge result because cables was vey good . Stock cables is 7 mm

<the ones with coil right above the spark plug like M156 , is not for them this message..and i dont have knowledge in that type,when they ready for change or not.

tziady

Can you suggest what wires to purchase for 2007 SL550? WEhat is the FCP part or other part recommended?

Thanks,
T

tonylinc

A 2007 SL550 does not have spark plug wires!!! None. Thank God! A quick look at the engine with the air filter case off the top of the motor, you'll see there are eight ignition coils each held on by two screws. Under each of those is a spark plug. Changing spark plugs and/or coils on these engines is like the simplest job in the world. Just don't drop or lose the screws that hold the coils. And don't over-tighten the spark plugs. Don't strip the threads! In earlier post I talked about which NGK spark plug to use, they are a NGK laser platinum PLKR6A, and I bought mine from NGK dot com. There is no reason under the sun to use any other plug not even a Bosch. I have mechanic friends who say they've seen the Bosch ceramic parts break; this may be superstition but I also have the original owner book that came with my 07 SL550 and it says NGK platinum PLKR6A so why monkey around using anything else? When I order from NGK, I specify. "NO Substitutes". And I get the right plugs. Mercedes, out of all the cars in the world are finicky about wrong spark plugs, the 1980s- 90s models more than others. All you need for total ignition tune up on a SL550 made in 2007 is plugs and coils. Coils, I believe the original ones are Delphi brand, that's what I've found on all my Benzos and I think they were original unless they'd been replaced already which I doubt. I bought replacements for about $30 each, pretty cheap when you consider that you want perfect-est combustion for the most power and economy. You can get them from FCPeuro, AutohausAZ, or even Amazon. Once you've replaced both the plugs and coils you are not going to have to think about them again for at least another 40,000 miles. Even if you don't get error codes indicating misfires, new coils should produce a better spark and make the engine run better and smoother and make more power.

Tommyboy928

we AMG guys got from this guy , https://www.formulapower.com/?s=merc...t_type=product need check if have for your car .

tonylinc

Anyone with a 2007 SL550 who has spark plug wires I would sure like to see those spark plug wires! They do not exist, unless you are referring to the engine wiring harness which should never need replacement, unless you're talking about the mid-1990s when they had the wire harness defect insulation issue! There simply are no spark plug wires when each coil is right on top of its very own spark plug.

tonylinc