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Okay: P0307 is only a single cylinder misfiring... not the whole bank off.
It can still be couple things:
bad ignition
(bad injector)
(bad cylinder)
Likely heat soaked coil...
Once proven bad, replace all 8x coil identical to fire exactly with the same voltage, at the same time.
(FYI: Injector gets halted as ECU recognize low contribution)
Repair is Not one coil + one plug... 8x of everything.: coils + boots + plugs
The underlaying troublemaker is stored extreme heat soaking heads at engine stops.
Last edited by CaliBenzDriver; Apr 13, 2026 at 02:45 PM.
Okay ! P0307 is only a single cylinder misfiring....
that is not the whole bank2.
It can still be a few things:
bad ignition
bad injector
bad cylinder
Likely heat soaked coil...
Once proven bad, replace all 8x coil identical to fire exactly with the same voltage, at the same time.
(FYI: Injector gets halted as ECU recognize low contribution)
Repair is Not one coil + one plug... 8x of everything.: coils + boots + plugs
Got it. It also smells like gas. My euroshop is 15 miles away, i am thinking i will just drive...
Got it. It also smells like gas. My euroshop is 15 miles away, i am thinking i will just drive...
yes, that's very reasonable.
> Smell of gas... heat soaked rail!
-- Can you hear your engine hissing 10mn after shutdown??
-- That is the overheated 3000Psi fuel rail off gasing back into tank that blows up tank seals or EVAP relief.
Flammable gas leak should be your top priority, right ?!
Last edited by CaliBenzDriver; Apr 13, 2026 at 03:07 PM.
> Smell of gas... heat soaked rail!
-- Can you hear your engine hissing 10mn after shutdown??
-- That is the overheated 3000Psi fuel rail off gasing back into tank that blows up tank seals or EVAP relief.
Flammable gas leak should be your top priority, right ?!
No engine hissing. Car drove perfectly fine, no spikes in engine temp. Only when it came to traffic stops, it was vibrating and stuttering. Euro shop thinks it could simply be the spark plugs.
It was the ignition coil that failed causing cylinder 7 to miss fire. Apprently spark plugs were changed only 6K miles back so I ened up changing all the coils. Warranty covered a little bit and my net out of pocket was 2440.
Got the service A due in July
It was the ignition coil that failed causing cylinder 7 to miss fire. Apprently spark plugs were changed only 6K miles back so I ened up changing all the coils. Warranty covered a little bit and my net out of pocket was 2440.
Got the service A due in July
Invoice details show only HALF the 8 coils got replaced, right?
Invoice details show only HALF the 8 coils got replaced, right?
QTY 4Pcs
Keep that record in mind.
Mechanic said only 4 coils are needed for this V8 because engine is split in two banks 2 per 4cycl on each bank. Dont know what that means but ChatGPT seems to agee
Mechanic said only 4 coils are needed for this V8 because engine is split in two banks 2 per 4cycl on each bank. Dont know what that means but ChatGPT seems to agee
Your two banks of coils fire up as follow:
M177 firing order: 1 - 5 - 4 - 2 - 6 - 3 - 7 - 8
The timing of both banks are mixed together :
Bk1 Bk2 Bk1 Bk1 Bk2 Bk1 Bk2Bk2
With 7 years difference old vs. new coils put out different high voltage. That ignite with slightly different delays. That is ok but not best for ECU timing work. New coils will fire a hair sooner than older ones. ECU will adapt to engine.
The rational is you shall be replacing remaining over heated coils within a year or two and you better match exact same one, not just new ones.
Retail M177 MB.coil : $428 Ea.
At that price point... don't worry mixing old + new coils. It is done everyday everywhere - A common practice.
Last edited by CaliBenzDriver; Apr 16, 2026 at 04:57 PM.
The timing of both banks are mixed together :
Bk1 Bk2 Bk1 Bk1 Bk2 Bk1 Bk2Bk2
With 7 years difference old vs. new coils put out different high voltage. That ignite with slightly different delays. That is ok but not best for ECU timing work. New coils will fire a hair sooner than older ones. ECU will adapt to engine.
Retail M177 MB.coil : $428 Ea.
The rational is you shall be replacing remaining over heated coils within a year or two.
Oh boy so another 2700 another ?
idk seems like this euro shops always screws me over..will have to find another place or go to the stealership to see what they have to offer.
I also didn’t appreciate the breakdown they gave regarding wary coverage. I have a $500 deductible and then the warranty kicks. Got a very good warranty that covered 100% of my RMS leak cost.
For this repair because only 1 of the coil was broken, the shop said warranty would only cover that + some labor.
An expensive hobby to own this car but I love it. Hoping to get an S65 sometime soon.
Oh boy so another 2700 another ?
idk seems like this euro shops always screws me over..will have to find another place or go to the stealership to see what they have to offer.
I also didn’t appreciate the breakdown they gave regarding wary coverage. I have a $500 deductible and then the warranty kicks. Got a very good warranty that covered 100% of my RMS leak cost.
For this repair because only 1 of the coil was broken, the shop said warranty would only cover that + some labor.
An expensive hobby to own this car but I love it. Hoping to get an S65 sometime soon.
I can see warranty covering only 1 single coil... that's part of the exclusions in the fine prints.
At over $400.Ea... I think you can shop around for a substantial discount genuine NIB parts.
Same brand same P/N... then go for it - If not it will work nearly as well until time comes for other bank misfires.
Last edited by CaliBenzDriver; Apr 16, 2026 at 05:24 PM.
I can see warranty covering only 1 single coil... that's part of the exclusions in the fine prints.
At over $400.Ea... I think you can shop around to find a 40% discount for genuine parts.
Same brand same P/N... then go for it - If not it will work nearly as well until time comes for other bank misfires.
Here’s the problem with owning a Mercedes: Either you don’t care how much it costs to own, or you learn to do stuff yourself. Lots of people think that if you own a late model Mercedes, especially an AMG car, you fit into the first category. Always, always, always ask for a detailed estimate up front. Then, do some homework. I know it is easier to have everything fixed at once, but you will pay for the convenience.
From FCP’s website, it appears a single coil assembly supports two plugs. I don’t know the complexity of swapping out coils on your engine, but certainly you were screwed on the price for the coils. I would get a quote from the Mercedes dealer for the parts.
The “good news” is that it appears all of your coils assemblies (4) were replaced.
Last edited by PotatoHeadII; Apr 17, 2026 at 08:30 AM.
Here’s the problem with owning a Mercedes: Either you don’t care how much it costs to own, or you learn to do stuff yourself. Lots of people think that if you own a late model Mercedes, especially an AMG car, you fit into the first category. Always, always, always ask for a detailed estimate up front. Then, do some homework. I know it is easier to have everything fixed at once, but you will pay for the convenience.
From FCP’s website, it appears a single coil assembly supports two plugs. I don’t know the complexity of swapping out coils on your engine, but certainly you were screwed on the price for the coils. I would get a quote from the Mercedes dealer for the parts.
The “good news” is that it appears all of your coils assemblies (4) were replaced.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
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