benz_addict

Got it tuned this year in January. Right after the tune, as expected, car started misfiring badly. Was told it was the transformer so I changed that out but still misfired. Changed out the 24 spark plugs with OEM NGK plugs from the dealer as well as the drivers side coil pack and NO misfire.



This car is a undefeated rocket ship.

However, it started misfiring again this month. This time random misfire, mostly on cylinder 5 (what's up with cyl 5 misfiring on S600's???) so I changed out the coil pack as it's only been 10,000kms on the new plugs I thought. Misfire again with the new coil (passenger side this time).

Pulled out the plugs this is the condition of a tuned V12 plug after 10,000kms of hard driving.



Keep in mind each coil here costs around $1500, transformer is $1500 and 24 plugs are $400. This is some serious maintenance, thinking of going back to stock or doing a dyno-tune, I just want to extend the life of the plugs and coils as I don't want to change them each time I change my engine oil.

AMG-Driver

Thanks for your feedback. There is something wrong for sure. lean issue? Although the plug looks very dark the electrode seems to be really melted?

Can you please tell us a little more about your modifications, only ECU-Tune?

benz_addict

ECU/TCU tune, cat-less downpipes and 3" exhaust. Smells horrible even inside the cabin after a full throttle run. Of-course, this is only a bench tune. I'm not convinced if there is something wrong, or perhaps a sacrifice rather to have massive amounts of power vs sooner maintenance (especially turbo'd tuned cars). Power is there, also fuel economy and exhaust tips usually cake over to black.

AMG-Driver

From my experience with an ECU-tune the Plugs should not look that bad after 10.000 KM.

On my old SL600 with ECU-Tune we also changed the Fuel-Pump to the Sl65 Pump to be safe on Highspeed runs on the German Autobahn. Don't know if this effects also your driving-cycles, but the 65 pump has more capacity than the 600 Pump.

I would also check IAT, because if they are too high, the ECU possibly can not pull back enough timing with the ECU-Tune. But you say the car is running strong, so that might not be the problem.

For the smell in the cabin, is there a downpipe/exhaust leak?

TwinTurboTim

That looks like oil deposits. I would do a compression test for sure. A car that is lean will run good up til the point of melt down. Any other plugs look like that?

kamilclk430

I believe the Coils will last once you put the new ones in. They are good for some miles, plus they are way cheaper now than they use to be back in the day. I'm going to Speedriven today to scan the car after work for my current misfire issues. If I'm doing the coils which 99% of the chance I am I will go ahead and do the plugs as well on the car that way I can take a pic of what mine look like. The car probably has around 5K or more miles on the tune for sure. The other mods maybe 1K miles or so.

shardul

iTrader: (1)

high mileage 600 block are know to have scoring

my plug looked like that on cylinder 6 last year. I had to swap the engine

TwinTurboTim

Damn Shardul, can I ask what you paid for a motor?

RaceHorse

OP, how many miles on your car? What do the other plugs look like? I would think a box tune would treat all the plugs the same. Shardul, do you think the amg set up of spraying the cylinders with oil helps with the scoring or just delays the inevitable?

shardul

iTrader: (1)

it is only the 600s that have this issue. never seen it happen on a 65

RaceHorse

Good to know, thanks

driveability

That's oil, and rich.
I have to wonder If its too rich ? Any engine can pass oil by the rings, normally its one or two cylinders (V12 maybe 3). If all look like that investigate other areas of leakage. Guides, intake gaskets, PCV etc.
IMO

AMG-Driver

Yes its rich, but does the electrode really melt with rich? Maybe here are 2 things cumming together. Rich from normal driving or oil deposits and an additonal lean issue on WOT. Most important is to look at the the other plugs...Good luck!

TwinTurboTim

Just do a compression check for us or if you have access to a cylinder leakage tester. I would love to see your results. Then we can stop speculation. Oh and after you look at all the plugs.

Thericker

Also get it Dyno tuned vs box tuned, you mentioned having catless dwn pipes this will effect tune (to the LEAN side, I know we're talking about very possible RICH condition, but those melted sparkplugs scream LEAN too)

Exotic-metal55

Just do a leakdown test before anyting esle, to amke sure engine compression is ok and no further damage.

VMAX7

Im curious to know whats up with your 600.