Terry_mickie

Hello Benz family! I have an issue and I hope I can find the answer here. I own a 2007 S600 and I have a misfire on cylinder 6. New, correct plugs, new coil, newish but working voltage transformer and new O2 sensors.

What am I missing? What else could cause a misfire on just one cylinder?

DaleB

Coil pack. Been there, done that. It was #9 for me.

jmirgy

Also swap that coil pack with another and see if the fault moves to the cylinder with the suspect lead ?

Quick way to fault find....

DaleB

It would be, but you can't really do that on an S600. Each bank has a single coil pack for 12 plugs (6 cylinders) and they're not interchangeable. Or cheap.

jmirgy

OK, good call.

Could you swap the existing 2 packs with each other? To obtain the same effect ??

DaleB

Nope. They're unique mechanically, can't physically be swapped. Wouldn't that have been a great engineering choice, though?

jmirgy

Ah well..... More fool me for trying to introduce common sense...........

EasyPhil

Maybe you can swap the new defective one with the old to verify they are defective in different places?

lkchris

What else can cause a misfire?

… a fuel/air mixture so weak or so rich it cannot be ignited. This is obviously not an ignition system problem, but can be something like a vacuum leak, malfunctioning MAF sensor, etc.

Given what merikuns call multipoint injection, fueling mechanics are not so likely, but it’s certainly possible for not all cylinders to be equally mechanically sound and a weak one may be susceptible to misfiring (first). Perhaps think testing compression.

DaleB

It is possible that he could have a bad injector, a burned valve, a worn cam lobe or something of that sort. The body of data available for this particular instance (early production S600 with a single cylinder misfire) would indicate it's likely a coil pack. I had a persistent #9 misfire... shipped both packs off to Clark for rebuild, replaced the VT, still had a #9 misfire that I spent months trying to troubleshoot because, hey, I couldn't have possibly gotten TWO coil packs failing on #9, right?

Finally shipped the left bank pack back to Clark. Intermittent #9 failure, he fixed it under warranty, I wrote off the months of trying to fix a nonexistent fuel or air problem. On the bright side, I did find and fix a few bad vacuum lines along the way, and installed some silicone turbo-intercooler hoses that were much better than stock, so there's that.

To the OP, if you haven't run a few bottles of injector cleaner through it yet, you could try that.

konigstiger

MB released bulletin addressing wiring harness ground concern that 'may' apply.

BOTUS

that's a nasty design feature....